There was a system called "tabs" at that candy store.

The elderly shopkeeper, who had lost confidence in her memory, recorded in a ledger which child bought what on their tab.

One day, a mischievous child secretly changed the ledger, throwing the candy store into chaos.

To prevent this from happening again, the children who wished for peace in the candy store decided to manage the tab information not just by the old lady, but by all the children.

Everyone had a ledger, ensuring that the "same information" existed "simultaneously in multiple copies."

Furthermore, they decided on a rule that when updating the information, at least half of the ledger owners had to verify it first.

This way, even if a mischievous child tried to change the ledger again, the correct information would never be lost.

"――Well, this is a rough idea of how blockchain technology, used in things like Bitcoin, works. There are various mechanisms necessary to make this work, like giving candy to the child who creates a new page in the ledger... Anyway, the advantage is that there's no risk of direct hacking."

Mitsuhiro Akutagawa, who said this, received a serious nod from Nana Shiga in front of him.

"It's great that the kind old lady's store that allows tabs for children is protected...!"

"Yeah... even though it's just a store in an analogy."

"Ah, but I think I 'probably' understood the explanation!"

"I'm glad. So... what I'm curious about is why 'Satoshi Nakamoto' created this system and released it into the world without revealing who they are..."

Mitsuhiro lowered his eyes to the screen of his smartphone and continued as if talking to the person on the other side of the displayed text.

"I feel like there's a big hint in there..."

The opened messaging app showed only the words "Light to the future" in a faint light.

One month earlier――

Calm-colored curtains and rugs, a beautiful wooden table, a soft and carefully selected sofa.

The living room had been carefully arranged for a comfortable day off since Mitsuhiro became a salaryman. Although he no longer had the luxury of being particular about the materials due to certain circumstances, enjoying tea and his favorite classical music in this space was his modest pleasure after days of hard work.

...However.

"...What?"

Speaking with an undisguisedly grumpy tone, Mitsuhiro addressed the man who had suddenly called him.

"Hey, I know it's sudden, but I've got a favor to ask. Right now..."

"I'm on a day off, you know."

As the man tried to explain something, Mitsuhiro hurriedly interrupted him. It couldn't be helped; his coworker, Ryosuke Izumi, always brought up favors that were never good.

"Can't it wait until I go to work tomorrow?"

"I can't explain why, but it's super urgent! So I'm heading over now, okay?"

"Wait, hold on... ah."

Ignoring Mitsuhiro's attempts to refuse, Ryosuke unilaterally rattled off his request and ended the call.

"He never listens to people..."

Although Ryosuke was a troublesome person, it was also Mitsuhiro's fault for not choosing to ignore the call. Giving up on leisurely enjoying his music, Mitsuhiro prepared cups for Ryosuke and whoever he would likely bring along with his "favor."

"...So,"

Mitsuhiro sighed as he faced the two guests sitting on the sofa opposite him.

"Is that the 'urgent matter that can't tell the reason'?"

"I'm sorry! I never thought it would come to this..."

Nana apologized, looking regretful, but Mitsuhiro offered her a resigned smile, saying, "It's not your fault."

As Mitsuhiro had predicted, Ryosuke appeared with a woman by his side. What was unexpected, however, was that she was someone they knew.

"Ms. Shiga?"

"Do you know each other?"

Surprised by their reactions, Ryosuke looked curiously between Mitsuhiro and Nana. The two in question exchanged glances, unsure of how to explain their relationship.

They were not friends, but their relationship was deeper than mere acquaintances. In fact, there was a significant connection to Mitsuhiro's family, but he had no intention of explaining his personal affairs to Ryosuke, who was just a coworker.

"Uh... well, yeah, something like that."

Nana also seemed to sense Mitsuhiro's thoughts and was struggling to figure out how to explain their relationship. However, Ryosuke seemed to have no interest in the matter and simply laughed, saying, "Well, that works out perfectly."

"A guy from my client's sports equipment manufacturer told me there's an employee having trouble with insurance and asked if I could at least hear them out."

"...So why did you bring her to my house?"

"Well, it's best to talk to the person directly when discussing such things, right?"

While Ryosuke's reasoning seemed logical, Mitsuhiro couldn't help but suspect that he just found it too bothersome to handle the matter himself. However, Ryosuke showed no signs of embarrassment and even remarked, "It's a good way to pass the time, isn't it?"

"You're always just lazing around at home on your days off, aren't you?"

"...I'm not exactly lazing around, nor am I just killing time."

"Not killing time? Could it be related to that? Are you searching for that code too?"

"The Code Hunt" refers to the treasure hunt that stirred up the internet a year ago.

It was said that anyone who collected secret words hidden in various locations could amass a vast fortune.

The amount? Approximately 3.2 trillion yen—an amount large enough to host the Olympics.

The organizer, "Satoshi Nakamoto," is the anonymous genius who created the world's first cryptocurrency, Bitcoin.

Satoshi Nakamoto suddenly appeared on the internet, announced cryptocurrency technology, and then disappeared after April 2011.

With their untouched, immensely valuable Bitcoin, over a decade passed. A year ago, Satoshi Nakamoto reappeared on social media.

After actually moving their Bitcoin holdings and proving their authenticity, Satoshi Nakamoto declared, "I will give away all of my Bitcoin holdings to the person who collects all the codes" and then vanished once again.

"It's been a year since then. Are there even people who still take that pie-in-the-sky story seriously?"

"That's why it's a good target. Less competition is better, right? Plus, you have a lot of weird knowledge and you love solving mysteries."

"...Let's put that aside for now."

Worried that he might be roped into helping, Mitsuhiro shifted the conversation back and turned his gaze to the luggage Nana was carrying.

"Is this the 'urgent matter that can't tell the reason'?"

"If I didn't say that, you wouldn't take it, would you?"

"Of course not, it's my day off."

Mitsuhiro let out an obvious sigh, having been pushed around by this guy so many times. Ryosuke always easily accepts requests and troubles from his clients, and Mitsuhiro can't completely ignore it since it sometimes leads to actual work, albeit very rarely.

(But... this time, it's clearly a miss.)

Mitsuhiro shot a sharp glare at Ryosuke, who must have realized that, which is why he didn't talk about the reason earlier.

"Why do you always agree to things so easily?"

"When we're in trouble, we help each other out, right?"

"But I'm the one who's always solving the problems."

"Hey! Listen!"

Sensing the increasingly tense atmosphere between them, Nana forcefully stepped in.

"Can we at least hear the story?"

"Ah... yeah, sure."

Mitsuhiro reluctantly agreed to Nana's proposal, but he had a feeling about what was to come from the size and shape of the package she was holding.

Nana opened the package on the table.

"This is..."

As Mitsuhiro expected, it was a painting. With a unique use of colors and a tacky frame, the oil painting seemed to be the work of an 18th-century artist. Nana explained that it had become a hot topic after an influencer mentioned it on social media. With few original pieces available, it was difficult to obtain the artwork even in famous galleries.

"So, you want to insure this painting, right?"

Mitsuhiro interrupted Nana, who was diligently reading a long memo.

"But why Ms. Shiga?"

"The owner was worried about it being stolen, and I was asked to help while we were discussing it..."

Apparently, the painting was forcibly handed over to Nana for "appraisal." Although she hesitated to contact Mitsuhiro directly for such a personal matter, it ended up reaching Ryosuke's ears, and he brought her here. With a wry smile, Mitsuhiro had no choice but to address the situation.

"It would probably be covered under a movable property comprehensive insurance... it might be a one-time payment, though. Is that okay?"

"Is it going to be expensive?"

Mitsuhiro bowed his head in apology to Nana's anxious voice, saying, "Sorry, but I can't help with that. This is a job for an agent, not a head office salesperson like me."

"Didn't you like antiques? Can't you appraise it?"

"It's not my expertise. And the amount of insurance isn't always equal to the painting's price or value."

"I see..."

Disappointed by Nana's reaction, Mitsuhiro felt somewhat guilty, but if Ryosuke had listened properly from the beginning, there would have been no need for any wasted effort. With an internal sigh, Mitsuhiro continued while opening his notebook.

"Well, I know a few specialists, so I'll introduce you to a good insurance agency."

"Thank you very much!"

"As expected of Akutagawa, you're so reliable!"

Sighing for what felt like the umpteenth time today at the cheery tone of his colleagues, Mitsuhiro took a sip of his now lukewarm tea and spoke up.

"Still, it's quite something for someone to go as far as to insure a replica. They must really like the painting."

"Eh?"

Mitsuhiro's comment was met with surprised voices from both Nana and Ryosuke.

"A replica...!?"

"You didn't know?"

"I...I was told it's an original."

Seeing Nana's puzzled expression, Mitsuhiro furrowed his brow.

"Unfortunately, it seems like you've been sold a forgery."

Mitsuhiro's words were merciless.

"In that case, where it was purchased is the problem. I'd like to caution our business partners to avoid getting caught in the same situation, so if possible, could you ask the person to tell you about how they bought it?"

As Mitsuhiro's interest had already shifted elsewhere, Ryosuke stood up from the sofa, unable to hide his confusion.

"Hey, how did you know it wasn't the real deal?"

"Well, I thought it was suspicious because a person who would leave insuring their artwork to someone else probably wouldn't be able to easily obtain such a high-value piece. And, the frame is too old for an 18th-century artist, and the oil paint isn't degraded enough. The lack of even a single crack is unnatural... Whoever made this forgery might not be a professional. Excuse me a moment... Ah, as I thought."

Unaware of Nana's complicated expression at his harsh evaluation, Mitsuhiro tapped the frame with his finger. Ignoring the wide-eyed surprise of his two colleagues, Mitsuhiro flipped the painting over and removed the back of the frame, nodding to himself in understanding.

"This one was made quite recently."

"Recently!?"

With the two of them practically screaming, Mitsuhiro calmly continued his explanation.

"The canvas is brand new, isn't it? Someone probably saw that the painting had become popular and difficult to obtain, and thought they could make a profit by creating a replica... Hm?"

At that moment, as Mitsuhiro was examining the painting closely for any other oddities, he noticed something off.

"Did I just see something...?"

Looking more closely, Mitsuhiro realized that the raised paint in certain areas was catching the light and revealing some sort of shape. Sensing something intentional, Mitsuhiro tilted the painting at various angles, and the mystery presented itself to him with a certain regularity.

"Alphabet...? h...o..."

Mitsuhiro began to write the letters down on paper.

"howdo,youtrust... It's broken up in a strange way, but... How do you trust, maybe?"

"How do you trust?"

It was as if the message was directly questioning Mitsuhiro, and he found himself intrigued by the person who had embedded it.

The translation was almost 100% done by GPT-4, OpenAI’s large-scale language-generation model.

There was a system called "tabs" at that candy store.

The elderly shopkeeper, who had lost confidence in her memory, recorded in a ledger which child bought what on their tab.

One day, a mischievous child secretly changed the ledger, throwing the candy store into chaos.

To prevent this from happening again, the children who wished for peace in the candy store decided to manage the tab information not just by the old lady, but by all the children.

Everyone had a ledger, ensuring that the "same information" existed "simultaneously in multiple copies."

Furthermore, they decided on a rule that when updating the information, at least half of the ledger owners had to verify it first.

This way, even if a mischievous child tried to change the ledger again, the correct information would never be lost.

"――Well, this is a rough idea of how blockchain technology, used in things like Bitcoin, works. There are various mechanisms necessary to make this work, like giving candy to the child who creates a new page in the ledger... Anyway, the advantage is that there's no risk of direct hacking."

Mitsuhiro Akutagawa, who said this, received a serious nod from Nana Shiga in front of him.

"It's great that the kind old lady's store that allows tabs for children is protected...!"

"Yeah... even though it's just a store in an analogy."

"Ah, but I think I 'probably' understood the explanation!"

"I'm glad. So... what I'm curious about is why 'Satoshi Nakamoto' created this system and released it into the world without revealing who they are..."

Mitsuhiro lowered his eyes to the screen of his smartphone and continued as if talking to the person on the other side of the displayed text.

"I feel like there's a big hint in there..."

The opened messaging app showed only the words "Light to the future" in a faint light.

One month earlier――

Calm-colored curtains and rugs, a beautiful wooden table, a soft and carefully selected sofa.

The living room had been carefully arranged for a comfortable day off since Mitsuhiro became a salaryman. Although he no longer had the luxury of being particular about the materials due to certain circumstances, enjoying tea and his favorite classical music in this space was his modest pleasure after days of hard work.

...However.

"...What?"

Speaking with an undisguisedly grumpy tone, Mitsuhiro addressed the man who had suddenly called him.

"Hey, I know it's sudden, but I've got a favor to ask. Right now..."

"I'm on a day off, you know."

As the man tried to explain something, Mitsuhiro hurriedly interrupted him. It couldn't be helped; his coworker, Ryosuke Izumi, always brought up favors that were never good.

"Can't it wait until I go to work tomorrow?"

"I can't explain why, but it's super urgent! So I'm heading over now, okay?"

"Wait, hold on... ah."

Ignoring Mitsuhiro's attempts to refuse, Ryosuke unilaterally rattled off his request and ended the call.

"He never listens to people..."

Although Ryosuke was a troublesome person, it was also Mitsuhiro's fault for not choosing to ignore the call. Giving up on leisurely enjoying his music, Mitsuhiro prepared cups for Ryosuke and whoever he would likely bring along with his "favor."

"...So,"

Mitsuhiro sighed as he faced the two guests sitting on the sofa opposite him.

"Is that the 'urgent matter that can't tell the reason'?"

"I'm sorry! I never thought it would come to this..."

Nana apologized, looking regretful, but Mitsuhiro offered her a resigned smile, saying, "It's not your fault."

As Mitsuhiro had predicted, Ryosuke appeared with a woman by his side. What was unexpected, however, was that she was someone they knew.

"Ms. Shiga?"

"Do you know each other?"

Surprised by their reactions, Ryosuke looked curiously between Mitsuhiro and Nana. The two in question exchanged glances, unsure of how to explain their relationship.

They were not friends, but their relationship was deeper than mere acquaintances. In fact, there was a significant connection to Mitsuhiro's family, but he had no intention of explaining his personal affairs to Ryosuke, who was just a coworker.

"Uh... well, yeah, something like that."

Nana also seemed to sense Mitsuhiro's thoughts and was struggling to figure out how to explain their relationship. However, Ryosuke seemed to have no interest in the matter and simply laughed, saying, "Well, that works out perfectly."

"A guy from my client's sports equipment manufacturer told me there's an employee having trouble with insurance and asked if I could at least hear them out."

"...So why did you bring her to my house?"

"Well, it's best to talk to the person directly when discussing such things, right?"

While Ryosuke's reasoning seemed logical, Mitsuhiro couldn't help but suspect that he just found it too bothersome to handle the matter himself. However, Ryosuke showed no signs of embarrassment and even remarked, "It's a good way to pass the time, isn't it?"

"You're always just lazing around at home on your days off, aren't you?"

"...I'm not exactly lazing around, nor am I just killing time."

"Not killing time? Could it be related to that? Are you searching for that code too?"

"The Code Hunt" refers to the treasure hunt that stirred up the internet a year ago.

It was said that anyone who collected secret words hidden in various locations could amass a vast fortune.

The amount? Approximately 3.2 trillion yen—an amount large enough to host the Olympics.

The organizer, "Satoshi Nakamoto," is the anonymous genius who created the world's first cryptocurrency, Bitcoin.

Satoshi Nakamoto suddenly appeared on the internet, announced cryptocurrency technology, and then disappeared after April 2011.

With their untouched, immensely valuable Bitcoin, over a decade passed. A year ago, Satoshi Nakamoto reappeared on social media.

After actually moving their Bitcoin holdings and proving their authenticity, Satoshi Nakamoto declared, "I will give away all of my Bitcoin holdings to the person who collects all the codes" and then vanished once again.

"It's been a year since then. Are there even people who still take that pie-in-the-sky story seriously?"

"That's why it's a good target. Less competition is better, right? Plus, you have a lot of weird knowledge and you love solving mysteries."

"...Let's put that aside for now."

Worried that he might be roped into helping, Mitsuhiro shifted the conversation back and turned his gaze to the luggage Nana was carrying.

"Is this the 'urgent matter that can't tell the reason'?"

"If I didn't say that, you wouldn't take it, would you?"

"Of course not, it's my day off."

Mitsuhiro let out an obvious sigh, having been pushed around by this guy so many times. Ryosuke always easily accepts requests and troubles from his clients, and Mitsuhiro can't completely ignore it since it sometimes leads to actual work, albeit very rarely.

(But... this time, it's clearly a miss.)

Mitsuhiro shot a sharp glare at Ryosuke, who must have realized that, which is why he didn't talk about the reason earlier.

"Why do you always agree to things so easily?"

"When we're in trouble, we help each other out, right?"

"But I'm the one who's always solving the problems."

"Hey! Listen!"

Sensing the increasingly tense atmosphere between them, Nana forcefully stepped in.

"Can we at least hear the story?"

"Ah... yeah, sure."

Mitsuhiro reluctantly agreed to Nana's proposal, but he had a feeling about what was to come from the size and shape of the package she was holding.

Nana opened the package on the table.

"This is..."

As Mitsuhiro expected, it was a painting. With a unique use of colors and a tacky frame, the oil painting seemed to be the work of an 18th-century artist. Nana explained that it had become a hot topic after an influencer mentioned it on social media. With few original pieces available, it was difficult to obtain the artwork even in famous galleries.

"So, you want to insure this painting, right?"

Mitsuhiro interrupted Nana, who was diligently reading a long memo.

"But why Ms. Shiga?"

"The owner was worried about it being stolen, and I was asked to help while we were discussing it..."

Apparently, the painting was forcibly handed over to Nana for "appraisal." Although she hesitated to contact Mitsuhiro directly for such a personal matter, it ended up reaching Ryosuke's ears, and he brought her here. With a wry smile, Mitsuhiro had no choice but to address the situation.

"It would probably be covered under a movable property comprehensive insurance... it might be a one-time payment, though. Is that okay?"

"Is it going to be expensive?"

Mitsuhiro bowed his head in apology to Nana's anxious voice, saying, "Sorry, but I can't help with that. This is a job for an agent, not a head office salesperson like me."

"Didn't you like antiques? Can't you appraise it?"

"It's not my expertise. And the amount of insurance isn't always equal to the painting's price or value."

"I see..."

Disappointed by Nana's reaction, Mitsuhiro felt somewhat guilty, but if Ryosuke had listened properly from the beginning, there would have been no need for any wasted effort. With an internal sigh, Mitsuhiro continued while opening his notebook.

"Well, I know a few specialists, so I'll introduce you to a good insurance agency."

"Thank you very much!"

"As expected of Akutagawa, you're so reliable!"

Sighing for what felt like the umpteenth time today at the cheery tone of his colleagues, Mitsuhiro took a sip of his now lukewarm tea and spoke up.

"Still, it's quite something for someone to go as far as to insure a replica. They must really like the painting."

"Eh?"

Mitsuhiro's comment was met with surprised voices from both Nana and Ryosuke.

"A replica...!?"

"You didn't know?"

"I...I was told it's an original."

Seeing Nana's puzzled expression, Mitsuhiro furrowed his brow.

"Unfortunately, it seems like you've been sold a forgery."

Mitsuhiro's words were merciless.

"In that case, where it was purchased is the problem. I'd like to caution our business partners to avoid getting caught in the same situation, so if possible, could you ask the person to tell you about how they bought it?"

As Mitsuhiro's interest had already shifted elsewhere, Ryosuke stood up from the sofa, unable to hide his confusion.

"Hey, how did you know it wasn't the real deal?"

"Well, I thought it was suspicious because a person who would leave insuring their artwork to someone else probably wouldn't be able to easily obtain such a high-value piece. And, the frame is too old for an 18th-century artist, and the oil paint isn't degraded enough. The lack of even a single crack is unnatural... Whoever made this forgery might not be a professional. Excuse me a moment... Ah, as I thought."

Unaware of Nana's complicated expression at his harsh evaluation, Mitsuhiro tapped the frame with his finger. Ignoring the wide-eyed surprise of his two colleagues, Mitsuhiro flipped the painting over and removed the back of the frame, nodding to himself in understanding.

"This one was made quite recently."

"Recently!?"

With the two of them practically screaming, Mitsuhiro calmly continued his explanation.

"The canvas is brand new, isn't it? Someone probably saw that the painting had become popular and difficult to obtain, and thought they could make a profit by creating a replica... Hm?"

At that moment, as Mitsuhiro was examining the painting closely for any other oddities, he noticed something off.

"Did I just see something...?"

Looking more closely, Mitsuhiro realized that the raised paint in certain areas was catching the light and revealing some sort of shape. Sensing something intentional, Mitsuhiro tilted the painting at various angles, and the mystery presented itself to him with a certain regularity.

"Alphabet...? h...o..."

Mitsuhiro began to write the letters down on paper.

"howdo,youtrust... It's broken up in a strange way, but... How do you trust, maybe?"

"How do you trust?"

It was as if the message was directly questioning Mitsuhiro, and he found himself intrigued by the person who had embedded it.

The translation was almost 100% done by GPT-4, OpenAI’s large-scale language-generation model.

There was a system called "tabs" at that candy store.

The elderly shopkeeper, who had lost confidence in her memory, recorded in a ledger which child bought what on their tab.

One day, a mischievous child secretly changed the ledger, throwing the candy store into chaos.

To prevent this from happening again, the children who wished for peace in the candy store decided to manage the tab information not just by the old lady, but by all the children.

Everyone had a ledger, ensuring that the "same information" existed "simultaneously in multiple copies."

Furthermore, they decided on a rule that when updating the information, at least half of the ledger owners had to verify it first.

This way, even if a mischievous child tried to change the ledger again, the correct information would never be lost.

"――Well, this is a rough idea of how blockchain technology, used in things like Bitcoin, works. There are various mechanisms necessary to make this work, like giving candy to the child who creates a new page in the ledger... Anyway, the advantage is that there's no risk of direct hacking."

Mitsuhiro Akutagawa, who said this, received a serious nod from Nana Shiga in front of him.

"It's great that the kind old lady's store that allows tabs for children is protected...!"

"Yeah... even though it's just a store in an analogy."

"Ah, but I think I 'probably' understood the explanation!"

"I'm glad. So... what I'm curious about is why 'Satoshi Nakamoto' created this system and released it into the world without revealing who they are..."

Mitsuhiro lowered his eyes to the screen of his smartphone and continued as if talking to the person on the other side of the displayed text.

"I feel like there's a big hint in there..."

The opened messaging app showed only the words "Light to the future" in a faint light.

One month earlier――

Calm-colored curtains and rugs, a beautiful wooden table, a soft and carefully selected sofa.

The living room had been carefully arranged for a comfortable day off since Mitsuhiro became a salaryman. Although he no longer had the luxury of being particular about the materials due to certain circumstances, enjoying tea and his favorite classical music in this space was his modest pleasure after days of hard work.

...However.

"...What?"

Speaking with an undisguisedly grumpy tone, Mitsuhiro addressed the man who had suddenly called him.

"Hey, I know it's sudden, but I've got a favor to ask. Right now..."

"I'm on a day off, you know."

As the man tried to explain something, Mitsuhiro hurriedly interrupted him. It couldn't be helped; his coworker, Ryosuke Izumi, always brought up favors that were never good.

"Can't it wait until I go to work tomorrow?"

"I can't explain why, but it's super urgent! So I'm heading over now, okay?"

"Wait, hold on... ah."

Ignoring Mitsuhiro's attempts to refuse, Ryosuke unilaterally rattled off his request and ended the call.

"He never listens to people..."

Although Ryosuke was a troublesome person, it was also Mitsuhiro's fault for not choosing to ignore the call. Giving up on leisurely enjoying his music, Mitsuhiro prepared cups for Ryosuke and whoever he would likely bring along with his "favor."

"...So,"

Mitsuhiro sighed as he faced the two guests sitting on the sofa opposite him.

"Is that the 'urgent matter that can't tell the reason'?"

"I'm sorry! I never thought it would come to this..."

Nana apologized, looking regretful, but Mitsuhiro offered her a resigned smile, saying, "It's not your fault."

As Mitsuhiro had predicted, Ryosuke appeared with a woman by his side. What was unexpected, however, was that she was someone they knew.

"Ms. Shiga?"

"Do you know each other?"

Surprised by their reactions, Ryosuke looked curiously between Mitsuhiro and Nana. The two in question exchanged glances, unsure of how to explain their relationship.

They were not friends, but their relationship was deeper than mere acquaintances. In fact, there was a significant connection to Mitsuhiro's family, but he had no intention of explaining his personal affairs to Ryosuke, who was just a coworker.

"Uh... well, yeah, something like that."

Nana also seemed to sense Mitsuhiro's thoughts and was struggling to figure out how to explain their relationship. However, Ryosuke seemed to have no interest in the matter and simply laughed, saying, "Well, that works out perfectly."

"A guy from my client's sports equipment manufacturer told me there's an employee having trouble with insurance and asked if I could at least hear them out."

"...So why did you bring her to my house?"

"Well, it's best to talk to the person directly when discussing such things, right?"

While Ryosuke's reasoning seemed logical, Mitsuhiro couldn't help but suspect that he just found it too bothersome to handle the matter himself. However, Ryosuke showed no signs of embarrassment and even remarked, "It's a good way to pass the time, isn't it?"

"You're always just lazing around at home on your days off, aren't you?"

"...I'm not exactly lazing around, nor am I just killing time."

"Not killing time? Could it be related to that? Are you searching for that code too?"

"The Code Hunt" refers to the treasure hunt that stirred up the internet a year ago.

It was said that anyone who collected secret words hidden in various locations could amass a vast fortune.

The amount? Approximately 3.2 trillion yen—an amount large enough to host the Olympics.

The organizer, "Satoshi Nakamoto," is the anonymous genius who created the world's first cryptocurrency, Bitcoin.

Satoshi Nakamoto suddenly appeared on the internet, announced cryptocurrency technology, and then disappeared after April 2011.

With their untouched, immensely valuable Bitcoin, over a decade passed. A year ago, Satoshi Nakamoto reappeared on social media.

After actually moving their Bitcoin holdings and proving their authenticity, Satoshi Nakamoto declared, "I will give away all of my Bitcoin holdings to the person who collects all the codes" and then vanished once again.

"It's been a year since then. Are there even people who still take that pie-in-the-sky story seriously?"

"That's why it's a good target. Less competition is better, right? Plus, you have a lot of weird knowledge and you love solving mysteries."

"...Let's put that aside for now."

Worried that he might be roped into helping, Mitsuhiro shifted the conversation back and turned his gaze to the luggage Nana was carrying.

"Is this the 'urgent matter that can't tell the reason'?"

"If I didn't say that, you wouldn't take it, would you?"

"Of course not, it's my day off."

Mitsuhiro let out an obvious sigh, having been pushed around by this guy so many times. Ryosuke always easily accepts requests and troubles from his clients, and Mitsuhiro can't completely ignore it since it sometimes leads to actual work, albeit very rarely.

(But... this time, it's clearly a miss.)

Mitsuhiro shot a sharp glare at Ryosuke, who must have realized that, which is why he didn't talk about the reason earlier.

"Why do you always agree to things so easily?"

"When we're in trouble, we help each other out, right?"

"But I'm the one who's always solving the problems."

"Hey! Listen!"

Sensing the increasingly tense atmosphere between them, Nana forcefully stepped in.

"Can we at least hear the story?"

"Ah... yeah, sure."

Mitsuhiro reluctantly agreed to Nana's proposal, but he had a feeling about what was to come from the size and shape of the package she was holding.

Nana opened the package on the table.

"This is..."

As Mitsuhiro expected, it was a painting. With a unique use of colors and a tacky frame, the oil painting seemed to be the work of an 18th-century artist. Nana explained that it had become a hot topic after an influencer mentioned it on social media. With few original pieces available, it was difficult to obtain the artwork even in famous galleries.

"So, you want to insure this painting, right?"

Mitsuhiro interrupted Nana, who was diligently reading a long memo.

"But why Ms. Shiga?"

"The owner was worried about it being stolen, and I was asked to help while we were discussing it..."

Apparently, the painting was forcibly handed over to Nana for "appraisal." Although she hesitated to contact Mitsuhiro directly for such a personal matter, it ended up reaching Ryosuke's ears, and he brought her here. With a wry smile, Mitsuhiro had no choice but to address the situation.

"It would probably be covered under a movable property comprehensive insurance... it might be a one-time payment, though. Is that okay?"

"Is it going to be expensive?"

Mitsuhiro bowed his head in apology to Nana's anxious voice, saying, "Sorry, but I can't help with that. This is a job for an agent, not a head office salesperson like me."

"Didn't you like antiques? Can't you appraise it?"

"It's not my expertise. And the amount of insurance isn't always equal to the painting's price or value."

"I see..."

Disappointed by Nana's reaction, Mitsuhiro felt somewhat guilty, but if Ryosuke had listened properly from the beginning, there would have been no need for any wasted effort. With an internal sigh, Mitsuhiro continued while opening his notebook.

"Well, I know a few specialists, so I'll introduce you to a good insurance agency."

"Thank you very much!"

"As expected of Akutagawa, you're so reliable!"

Sighing for what felt like the umpteenth time today at the cheery tone of his colleagues, Mitsuhiro took a sip of his now lukewarm tea and spoke up.

"Still, it's quite something for someone to go as far as to insure a replica. They must really like the painting."

"Eh?"

Mitsuhiro's comment was met with surprised voices from both Nana and Ryosuke.

"A replica...!?"

"You didn't know?"

"I...I was told it's an original."

Seeing Nana's puzzled expression, Mitsuhiro furrowed his brow.

"Unfortunately, it seems like you've been sold a forgery."

Mitsuhiro's words were merciless.

"In that case, where it was purchased is the problem. I'd like to caution our business partners to avoid getting caught in the same situation, so if possible, could you ask the person to tell you about how they bought it?"

As Mitsuhiro's interest had already shifted elsewhere, Ryosuke stood up from the sofa, unable to hide his confusion.

"Hey, how did you know it wasn't the real deal?"

"Well, I thought it was suspicious because a person who would leave insuring their artwork to someone else probably wouldn't be able to easily obtain such a high-value piece. And, the frame is too old for an 18th-century artist, and the oil paint isn't degraded enough. The lack of even a single crack is unnatural... Whoever made this forgery might not be a professional. Excuse me a moment... Ah, as I thought."

Unaware of Nana's complicated expression at his harsh evaluation, Mitsuhiro tapped the frame with his finger. Ignoring the wide-eyed surprise of his two colleagues, Mitsuhiro flipped the painting over and removed the back of the frame, nodding to himself in understanding.

"This one was made quite recently."

"Recently!?"

With the two of them practically screaming, Mitsuhiro calmly continued his explanation.

"The canvas is brand new, isn't it? Someone probably saw that the painting had become popular and difficult to obtain, and thought they could make a profit by creating a replica... Hm?"

At that moment, as Mitsuhiro was examining the painting closely for any other oddities, he noticed something off.

"Did I just see something...?"

Looking more closely, Mitsuhiro realized that the raised paint in certain areas was catching the light and revealing some sort of shape. Sensing something intentional, Mitsuhiro tilted the painting at various angles, and the mystery presented itself to him with a certain regularity.

"Alphabet...? h...o..."

Mitsuhiro began to write the letters down on paper.

"howdo,youtrust... It's broken up in a strange way, but... How do you trust, maybe?"

"How do you trust?"

It was as if the message was directly questioning Mitsuhiro, and he found himself intrigued by the person who had embedded it.

The translation was almost 100% done by GPT-4, OpenAI’s large-scale language-generation model.

There was a system called "tabs" at that candy store.

The elderly shopkeeper, who had lost confidence in her memory, recorded in a ledger which child bought what on their tab.

One day, a mischievous child secretly changed the ledger, throwing the candy store into chaos.

To prevent this from happening again, the children who wished for peace in the candy store decided to manage the tab information not just by the old lady, but by all the children.

Everyone had a ledger, ensuring that the "same information" existed "simultaneously in multiple copies."

Furthermore, they decided on a rule that when updating the information, at least half of the ledger owners had to verify it first.

This way, even if a mischievous child tried to change the ledger again, the correct information would never be lost.

"――Well, this is a rough idea of how blockchain technology, used in things like Bitcoin, works. There are various mechanisms necessary to make this work, like giving candy to the child who creates a new page in the ledger... Anyway, the advantage is that there's no risk of direct hacking."

Mitsuhiro Akutagawa, who said this, received a serious nod from Nana Shiga in front of him.

"It's great that the kind old lady's store that allows tabs for children is protected...!"

"Yeah... even though it's just a store in an analogy."

"Ah, but I think I 'probably' understood the explanation!"

"I'm glad. So... what I'm curious about is why 'Satoshi Nakamoto' created this system and released it into the world without revealing who they are..."

Mitsuhiro lowered his eyes to the screen of his smartphone and continued as if talking to the person on the other side of the displayed text.

"I feel like there's a big hint in there..."

The opened messaging app showed only the words "Light to the future" in a faint light.

One month earlier――

Calm-colored curtains and rugs, a beautiful wooden table, a soft and carefully selected sofa.

The living room had been carefully arranged for a comfortable day off since Mitsuhiro became a salaryman. Although he no longer had the luxury of being particular about the materials due to certain circumstances, enjoying tea and his favorite classical music in this space was his modest pleasure after days of hard work.

...However.

"...What?"

Speaking with an undisguisedly grumpy tone, Mitsuhiro addressed the man who had suddenly called him.

"Hey, I know it's sudden, but I've got a favor to ask. Right now..."

"I'm on a day off, you know."

As the man tried to explain something, Mitsuhiro hurriedly interrupted him. It couldn't be helped; his coworker, Ryosuke Izumi, always brought up favors that were never good.

"Can't it wait until I go to work tomorrow?"

"I can't explain why, but it's super urgent! So I'm heading over now, okay?"

"Wait, hold on... ah."

Ignoring Mitsuhiro's attempts to refuse, Ryosuke unilaterally rattled off his request and ended the call.

"He never listens to people..."

Although Ryosuke was a troublesome person, it was also Mitsuhiro's fault for not choosing to ignore the call. Giving up on leisurely enjoying his music, Mitsuhiro prepared cups for Ryosuke and whoever he would likely bring along with his "favor."

"...So,"

Mitsuhiro sighed as he faced the two guests sitting on the sofa opposite him.

"Is that the 'urgent matter that can't tell the reason'?"

"I'm sorry! I never thought it would come to this..."

Nana apologized, looking regretful, but Mitsuhiro offered her a resigned smile, saying, "It's not your fault."

As Mitsuhiro had predicted, Ryosuke appeared with a woman by his side. What was unexpected, however, was that she was someone they knew.

"Ms. Shiga?"

"Do you know each other?"

Surprised by their reactions, Ryosuke looked curiously between Mitsuhiro and Nana. The two in question exchanged glances, unsure of how to explain their relationship.

They were not friends, but their relationship was deeper than mere acquaintances. In fact, there was a significant connection to Mitsuhiro's family, but he had no intention of explaining his personal affairs to Ryosuke, who was just a coworker.

"Uh... well, yeah, something like that."

Nana also seemed to sense Mitsuhiro's thoughts and was struggling to figure out how to explain their relationship. However, Ryosuke seemed to have no interest in the matter and simply laughed, saying, "Well, that works out perfectly."

"A guy from my client's sports equipment manufacturer told me there's an employee having trouble with insurance and asked if I could at least hear them out."

"...So why did you bring her to my house?"

"Well, it's best to talk to the person directly when discussing such things, right?"

While Ryosuke's reasoning seemed logical, Mitsuhiro couldn't help but suspect that he just found it too bothersome to handle the matter himself. However, Ryosuke showed no signs of embarrassment and even remarked, "It's a good way to pass the time, isn't it?"

"You're always just lazing around at home on your days off, aren't you?"

"...I'm not exactly lazing around, nor am I just killing time."

"Not killing time? Could it be related to that? Are you searching for that code too?"

"The Code Hunt" refers to the treasure hunt that stirred up the internet a year ago.

It was said that anyone who collected secret words hidden in various locations could amass a vast fortune.

The amount? Approximately 3.2 trillion yen—an amount large enough to host the Olympics.

The organizer, "Satoshi Nakamoto," is the anonymous genius who created the world's first cryptocurrency, Bitcoin.

Satoshi Nakamoto suddenly appeared on the internet, announced cryptocurrency technology, and then disappeared after April 2011.

With their untouched, immensely valuable Bitcoin, over a decade passed. A year ago, Satoshi Nakamoto reappeared on social media.

After actually moving their Bitcoin holdings and proving their authenticity, Satoshi Nakamoto declared, "I will give away all of my Bitcoin holdings to the person who collects all the codes" and then vanished once again.

"It's been a year since then. Are there even people who still take that pie-in-the-sky story seriously?"

"That's why it's a good target. Less competition is better, right? Plus, you have a lot of weird knowledge and you love solving mysteries."

"...Let's put that aside for now."

Worried that he might be roped into helping, Mitsuhiro shifted the conversation back and turned his gaze to the luggage Nana was carrying.

"Is this the 'urgent matter that can't tell the reason'?"

"If I didn't say that, you wouldn't take it, would you?"

"Of course not, it's my day off."

Mitsuhiro let out an obvious sigh, having been pushed around by this guy so many times. Ryosuke always easily accepts requests and troubles from his clients, and Mitsuhiro can't completely ignore it since it sometimes leads to actual work, albeit very rarely.

(But... this time, it's clearly a miss.)

Mitsuhiro shot a sharp glare at Ryosuke, who must have realized that, which is why he didn't talk about the reason earlier.

"Why do you always agree to things so easily?"

"When we're in trouble, we help each other out, right?"

"But I'm the one who's always solving the problems."

"Hey! Listen!"

Sensing the increasingly tense atmosphere between them, Nana forcefully stepped in.

"Can we at least hear the story?"

"Ah... yeah, sure."

Mitsuhiro reluctantly agreed to Nana's proposal, but he had a feeling about what was to come from the size and shape of the package she was holding.

Nana opened the package on the table.

"This is..."

As Mitsuhiro expected, it was a painting. With a unique use of colors and a tacky frame, the oil painting seemed to be the work of an 18th-century artist. Nana explained that it had become a hot topic after an influencer mentioned it on social media. With few original pieces available, it was difficult to obtain the artwork even in famous galleries.

"So, you want to insure this painting, right?"

Mitsuhiro interrupted Nana, who was diligently reading a long memo.

"But why Ms. Shiga?"

"The owner was worried about it being stolen, and I was asked to help while we were discussing it..."

Apparently, the painting was forcibly handed over to Nana for "appraisal." Although she hesitated to contact Mitsuhiro directly for such a personal matter, it ended up reaching Ryosuke's ears, and he brought her here. With a wry smile, Mitsuhiro had no choice but to address the situation.

"It would probably be covered under a movable property comprehensive insurance... it might be a one-time payment, though. Is that okay?"

"Is it going to be expensive?"

Mitsuhiro bowed his head in apology to Nana's anxious voice, saying, "Sorry, but I can't help with that. This is a job for an agent, not a head office salesperson like me."

"Didn't you like antiques? Can't you appraise it?"

"It's not my expertise. And the amount of insurance isn't always equal to the painting's price or value."

"I see..."

Disappointed by Nana's reaction, Mitsuhiro felt somewhat guilty, but if Ryosuke had listened properly from the beginning, there would have been no need for any wasted effort. With an internal sigh, Mitsuhiro continued while opening his notebook.

"Well, I know a few specialists, so I'll introduce you to a good insurance agency."

"Thank you very much!"

"As expected of Akutagawa, you're so reliable!"

Sighing for what felt like the umpteenth time today at the cheery tone of his colleagues, Mitsuhiro took a sip of his now lukewarm tea and spoke up.

"Still, it's quite something for someone to go as far as to insure a replica. They must really like the painting."

"Eh?"

Mitsuhiro's comment was met with surprised voices from both Nana and Ryosuke.

"A replica...!?"

"You didn't know?"

"I...I was told it's an original."

Seeing Nana's puzzled expression, Mitsuhiro furrowed his brow.

"Unfortunately, it seems like you've been sold a forgery."

Mitsuhiro's words were merciless.

"In that case, where it was purchased is the problem. I'd like to caution our business partners to avoid getting caught in the same situation, so if possible, could you ask the person to tell you about how they bought it?"

As Mitsuhiro's interest had already shifted elsewhere, Ryosuke stood up from the sofa, unable to hide his confusion.

"Hey, how did you know it wasn't the real deal?"

"Well, I thought it was suspicious because a person who would leave insuring their artwork to someone else probably wouldn't be able to easily obtain such a high-value piece. And, the frame is too old for an 18th-century artist, and the oil paint isn't degraded enough. The lack of even a single crack is unnatural... Whoever made this forgery might not be a professional. Excuse me a moment... Ah, as I thought."

Unaware of Nana's complicated expression at his harsh evaluation, Mitsuhiro tapped the frame with his finger. Ignoring the wide-eyed surprise of his two colleagues, Mitsuhiro flipped the painting over and removed the back of the frame, nodding to himself in understanding.

"This one was made quite recently."

"Recently!?"

With the two of them practically screaming, Mitsuhiro calmly continued his explanation.

"The canvas is brand new, isn't it? Someone probably saw that the painting had become popular and difficult to obtain, and thought they could make a profit by creating a replica... Hm?"

At that moment, as Mitsuhiro was examining the painting closely for any other oddities, he noticed something off.

"Did I just see something...?"

Looking more closely, Mitsuhiro realized that the raised paint in certain areas was catching the light and revealing some sort of shape. Sensing something intentional, Mitsuhiro tilted the painting at various angles, and the mystery presented itself to him with a certain regularity.

"Alphabet...? h...o..."

Mitsuhiro began to write the letters down on paper.

"howdo,youtrust... It's broken up in a strange way, but... How do you trust, maybe?"

"How do you trust?"

It was as if the message was directly questioning Mitsuhiro, and he found himself intrigued by the person who had embedded it.

The translation was almost 100% done by GPT-4, OpenAI’s large-scale language-generation model.

There was a system called "tabs" at that candy store.

The elderly shopkeeper, who had lost confidence in her memory, recorded in a ledger which child bought what on their tab.

One day, a mischievous child secretly changed the ledger, throwing the candy store into chaos.

To prevent this from happening again, the children who wished for peace in the candy store decided to manage the tab information not just by the old lady, but by all the children.

Everyone had a ledger, ensuring that the "same information" existed "simultaneously in multiple copies."

Furthermore, they decided on a rule that when updating the information, at least half of the ledger owners had to verify it first.

This way, even if a mischievous child tried to change the ledger again, the correct information would never be lost.

"――Well, this is a rough idea of how blockchain technology, used in things like Bitcoin, works. There are various mechanisms necessary to make this work, like giving candy to the child who creates a new page in the ledger... Anyway, the advantage is that there's no risk of direct hacking."

Mitsuhiro Akutagawa, who said this, received a serious nod from Nana Shiga in front of him.

"It's great that the kind old lady's store that allows tabs for children is protected...!"

"Yeah... even though it's just a store in an analogy."

"Ah, but I think I 'probably' understood the explanation!"

"I'm glad. So... what I'm curious about is why 'Satoshi Nakamoto' created this system and released it into the world without revealing who they are..."

Mitsuhiro lowered his eyes to the screen of his smartphone and continued as if talking to the person on the other side of the displayed text.

"I feel like there's a big hint in there..."

The opened messaging app showed only the words "Light to the future" in a faint light.

One month earlier――

Calm-colored curtains and rugs, a beautiful wooden table, a soft and carefully selected sofa.

The living room had been carefully arranged for a comfortable day off since Mitsuhiro became a salaryman. Although he no longer had the luxury of being particular about the materials due to certain circumstances, enjoying tea and his favorite classical music in this space was his modest pleasure after days of hard work.

...However.

"...What?"

Speaking with an undisguisedly grumpy tone, Mitsuhiro addressed the man who had suddenly called him.

"Hey, I know it's sudden, but I've got a favor to ask. Right now..."

"I'm on a day off, you know."

As the man tried to explain something, Mitsuhiro hurriedly interrupted him. It couldn't be helped; his coworker, Ryosuke Izumi, always brought up favors that were never good.

"Can't it wait until I go to work tomorrow?"

"I can't explain why, but it's super urgent! So I'm heading over now, okay?"

"Wait, hold on... ah."

Ignoring Mitsuhiro's attempts to refuse, Ryosuke unilaterally rattled off his request and ended the call.

"He never listens to people..."

Although Ryosuke was a troublesome person, it was also Mitsuhiro's fault for not choosing to ignore the call. Giving up on leisurely enjoying his music, Mitsuhiro prepared cups for Ryosuke and whoever he would likely bring along with his "favor."

"...So,"

Mitsuhiro sighed as he faced the two guests sitting on the sofa opposite him.

"Is that the 'urgent matter that can't tell the reason'?"

"I'm sorry! I never thought it would come to this..."

Nana apologized, looking regretful, but Mitsuhiro offered her a resigned smile, saying, "It's not your fault."

As Mitsuhiro had predicted, Ryosuke appeared with a woman by his side. What was unexpected, however, was that she was someone they knew.

"Ms. Shiga?"

"Do you know each other?"

Surprised by their reactions, Ryosuke looked curiously between Mitsuhiro and Nana. The two in question exchanged glances, unsure of how to explain their relationship.

They were not friends, but their relationship was deeper than mere acquaintances. In fact, there was a significant connection to Mitsuhiro's family, but he had no intention of explaining his personal affairs to Ryosuke, who was just a coworker.

"Uh... well, yeah, something like that."

Nana also seemed to sense Mitsuhiro's thoughts and was struggling to figure out how to explain their relationship. However, Ryosuke seemed to have no interest in the matter and simply laughed, saying, "Well, that works out perfectly."

"A guy from my client's sports equipment manufacturer told me there's an employee having trouble with insurance and asked if I could at least hear them out."

"...So why did you bring her to my house?"

"Well, it's best to talk to the person directly when discussing such things, right?"

While Ryosuke's reasoning seemed logical, Mitsuhiro couldn't help but suspect that he just found it too bothersome to handle the matter himself. However, Ryosuke showed no signs of embarrassment and even remarked, "It's a good way to pass the time, isn't it?"

"You're always just lazing around at home on your days off, aren't you?"

"...I'm not exactly lazing around, nor am I just killing time."

"Not killing time? Could it be related to that? Are you searching for that code too?"

"The Code Hunt" refers to the treasure hunt that stirred up the internet a year ago.

It was said that anyone who collected secret words hidden in various locations could amass a vast fortune.

The amount? Approximately 3.2 trillion yen—an amount large enough to host the Olympics.

The organizer, "Satoshi Nakamoto," is the anonymous genius who created the world's first cryptocurrency, Bitcoin.

Satoshi Nakamoto suddenly appeared on the internet, announced cryptocurrency technology, and then disappeared after April 2011.

With their untouched, immensely valuable Bitcoin, over a decade passed. A year ago, Satoshi Nakamoto reappeared on social media.

After actually moving their Bitcoin holdings and proving their authenticity, Satoshi Nakamoto declared, "I will give away all of my Bitcoin holdings to the person who collects all the codes" and then vanished once again.

"It's been a year since then. Are there even people who still take that pie-in-the-sky story seriously?"

"That's why it's a good target. Less competition is better, right? Plus, you have a lot of weird knowledge and you love solving mysteries."

"...Let's put that aside for now."

Worried that he might be roped into helping, Mitsuhiro shifted the conversation back and turned his gaze to the luggage Nana was carrying.

"Is this the 'urgent matter that can't tell the reason'?"

"If I didn't say that, you wouldn't take it, would you?"

"Of course not, it's my day off."

Mitsuhiro let out an obvious sigh, having been pushed around by this guy so many times. Ryosuke always easily accepts requests and troubles from his clients, and Mitsuhiro can't completely ignore it since it sometimes leads to actual work, albeit very rarely.

(But... this time, it's clearly a miss.)

Mitsuhiro shot a sharp glare at Ryosuke, who must have realized that, which is why he didn't talk about the reason earlier.

"Why do you always agree to things so easily?"

"When we're in trouble, we help each other out, right?"

"But I'm the one who's always solving the problems."

"Hey! Listen!"

Sensing the increasingly tense atmosphere between them, Nana forcefully stepped in.

"Can we at least hear the story?"

"Ah... yeah, sure."

Mitsuhiro reluctantly agreed to Nana's proposal, but he had a feeling about what was to come from the size and shape of the package she was holding.

Nana opened the package on the table.

"This is..."

As Mitsuhiro expected, it was a painting. With a unique use of colors and a tacky frame, the oil painting seemed to be the work of an 18th-century artist. Nana explained that it had become a hot topic after an influencer mentioned it on social media. With few original pieces available, it was difficult to obtain the artwork even in famous galleries.

"So, you want to insure this painting, right?"

Mitsuhiro interrupted Nana, who was diligently reading a long memo.

"But why Ms. Shiga?"

"The owner was worried about it being stolen, and I was asked to help while we were discussing it..."

Apparently, the painting was forcibly handed over to Nana for "appraisal." Although she hesitated to contact Mitsuhiro directly for such a personal matter, it ended up reaching Ryosuke's ears, and he brought her here. With a wry smile, Mitsuhiro had no choice but to address the situation.

"It would probably be covered under a movable property comprehensive insurance... it might be a one-time payment, though. Is that okay?"

"Is it going to be expensive?"

Mitsuhiro bowed his head in apology to Nana's anxious voice, saying, "Sorry, but I can't help with that. This is a job for an agent, not a head office salesperson like me."

"Didn't you like antiques? Can't you appraise it?"

"It's not my expertise. And the amount of insurance isn't always equal to the painting's price or value."

"I see..."

Disappointed by Nana's reaction, Mitsuhiro felt somewhat guilty, but if Ryosuke had listened properly from the beginning, there would have been no need for any wasted effort. With an internal sigh, Mitsuhiro continued while opening his notebook.

"Well, I know a few specialists, so I'll introduce you to a good insurance agency."

"Thank you very much!"

"As expected of Akutagawa, you're so reliable!"

Sighing for what felt like the umpteenth time today at the cheery tone of his colleagues, Mitsuhiro took a sip of his now lukewarm tea and spoke up.

"Still, it's quite something for someone to go as far as to insure a replica. They must really like the painting."

"Eh?"

Mitsuhiro's comment was met with surprised voices from both Nana and Ryosuke.

"A replica...!?"

"You didn't know?"

"I...I was told it's an original."

Seeing Nana's puzzled expression, Mitsuhiro furrowed his brow.

"Unfortunately, it seems like you've been sold a forgery."

Mitsuhiro's words were merciless.

"In that case, where it was purchased is the problem. I'd like to caution our business partners to avoid getting caught in the same situation, so if possible, could you ask the person to tell you about how they bought it?"

As Mitsuhiro's interest had already shifted elsewhere, Ryosuke stood up from the sofa, unable to hide his confusion.

"Hey, how did you know it wasn't the real deal?"

"Well, I thought it was suspicious because a person who would leave insuring their artwork to someone else probably wouldn't be able to easily obtain such a high-value piece. And, the frame is too old for an 18th-century artist, and the oil paint isn't degraded enough. The lack of even a single crack is unnatural... Whoever made this forgery might not be a professional. Excuse me a moment... Ah, as I thought."

Unaware of Nana's complicated expression at his harsh evaluation, Mitsuhiro tapped the frame with his finger. Ignoring the wide-eyed surprise of his two colleagues, Mitsuhiro flipped the painting over and removed the back of the frame, nodding to himself in understanding.

"This one was made quite recently."

"Recently!?"

With the two of them practically screaming, Mitsuhiro calmly continued his explanation.

"The canvas is brand new, isn't it? Someone probably saw that the painting had become popular and difficult to obtain, and thought they could make a profit by creating a replica... Hm?"

At that moment, as Mitsuhiro was examining the painting closely for any other oddities, he noticed something off.

"Did I just see something...?"

Looking more closely, Mitsuhiro realized that the raised paint in certain areas was catching the light and revealing some sort of shape. Sensing something intentional, Mitsuhiro tilted the painting at various angles, and the mystery presented itself to him with a certain regularity.

"Alphabet...? h...o..."

Mitsuhiro began to write the letters down on paper.

"howdo,youtrust... It's broken up in a strange way, but... How do you trust, maybe?"

"How do you trust?"

It was as if the message was directly questioning Mitsuhiro, and he found himself intrigued by the person who had embedded it.

The translation was almost 100% done by GPT-4, OpenAI’s large-scale language-generation model.

There was a system called "tabs" at that candy store.

The elderly shopkeeper, who had lost confidence in her memory, recorded in a ledger which child bought what on their tab.

One day, a mischievous child secretly changed the ledger, throwing the candy store into chaos.

To prevent this from happening again, the children who wished for peace in the candy store decided to manage the tab information not just by the old lady, but by all the children.

Everyone had a ledger, ensuring that the "same information" existed "simultaneously in multiple copies."

Furthermore, they decided on a rule that when updating the information, at least half of the ledger owners had to verify it first.

This way, even if a mischievous child tried to change the ledger again, the correct information would never be lost.

"――Well, this is a rough idea of how blockchain technology, used in things like Bitcoin, works. There are various mechanisms necessary to make this work, like giving candy to the child who creates a new page in the ledger... Anyway, the advantage is that there's no risk of direct hacking."

Mitsuhiro Akutagawa, who said this, received a serious nod from Nana Shiga in front of him.

"It's great that the kind old lady's store that allows tabs for children is protected...!"

"Yeah... even though it's just a store in an analogy."

"Ah, but I think I 'probably' understood the explanation!"

"I'm glad. So... what I'm curious about is why 'Satoshi Nakamoto' created this system and released it into the world without revealing who they are..."

Mitsuhiro lowered his eyes to the screen of his smartphone and continued as if talking to the person on the other side of the displayed text.

"I feel like there's a big hint in there..."

The opened messaging app showed only the words "Light to the future" in a faint light.

One month earlier――

Calm-colored curtains and rugs, a beautiful wooden table, a soft and carefully selected sofa.

The living room had been carefully arranged for a comfortable day off since Mitsuhiro became a salaryman. Although he no longer had the luxury of being particular about the materials due to certain circumstances, enjoying tea and his favorite classical music in this space was his modest pleasure after days of hard work.

...However.

"...What?"

Speaking with an undisguisedly grumpy tone, Mitsuhiro addressed the man who had suddenly called him.

"Hey, I know it's sudden, but I've got a favor to ask. Right now..."

"I'm on a day off, you know."

As the man tried to explain something, Mitsuhiro hurriedly interrupted him. It couldn't be helped; his coworker, Ryosuke Izumi, always brought up favors that were never good.

"Can't it wait until I go to work tomorrow?"

"I can't explain why, but it's super urgent! So I'm heading over now, okay?"

"Wait, hold on... ah."

Ignoring Mitsuhiro's attempts to refuse, Ryosuke unilaterally rattled off his request and ended the call.

"He never listens to people..."

Although Ryosuke was a troublesome person, it was also Mitsuhiro's fault for not choosing to ignore the call. Giving up on leisurely enjoying his music, Mitsuhiro prepared cups for Ryosuke and whoever he would likely bring along with his "favor."

"...So,"

Mitsuhiro sighed as he faced the two guests sitting on the sofa opposite him.

"Is that the 'urgent matter that can't tell the reason'?"

"I'm sorry! I never thought it would come to this..."

Nana apologized, looking regretful, but Mitsuhiro offered her a resigned smile, saying, "It's not your fault."

As Mitsuhiro had predicted, Ryosuke appeared with a woman by his side. What was unexpected, however, was that she was someone they knew.

"Ms. Shiga?"

"Do you know each other?"

Surprised by their reactions, Ryosuke looked curiously between Mitsuhiro and Nana. The two in question exchanged glances, unsure of how to explain their relationship.

They were not friends, but their relationship was deeper than mere acquaintances. In fact, there was a significant connection to Mitsuhiro's family, but he had no intention of explaining his personal affairs to Ryosuke, who was just a coworker.

"Uh... well, yeah, something like that."

Nana also seemed to sense Mitsuhiro's thoughts and was struggling to figure out how to explain their relationship. However, Ryosuke seemed to have no interest in the matter and simply laughed, saying, "Well, that works out perfectly."

"A guy from my client's sports equipment manufacturer told me there's an employee having trouble with insurance and asked if I could at least hear them out."

"...So why did you bring her to my house?"

"Well, it's best to talk to the person directly when discussing such things, right?"

While Ryosuke's reasoning seemed logical, Mitsuhiro couldn't help but suspect that he just found it too bothersome to handle the matter himself. However, Ryosuke showed no signs of embarrassment and even remarked, "It's a good way to pass the time, isn't it?"

"You're always just lazing around at home on your days off, aren't you?"

"...I'm not exactly lazing around, nor am I just killing time."

"Not killing time? Could it be related to that? Are you searching for that code too?"

"The Code Hunt" refers to the treasure hunt that stirred up the internet a year ago.

It was said that anyone who collected secret words hidden in various locations could amass a vast fortune.

The amount? Approximately 3.2 trillion yen—an amount large enough to host the Olympics.

The organizer, "Satoshi Nakamoto," is the anonymous genius who created the world's first cryptocurrency, Bitcoin.

Satoshi Nakamoto suddenly appeared on the internet, announced cryptocurrency technology, and then disappeared after April 2011.

With their untouched, immensely valuable Bitcoin, over a decade passed. A year ago, Satoshi Nakamoto reappeared on social media.

After actually moving their Bitcoin holdings and proving their authenticity, Satoshi Nakamoto declared, "I will give away all of my Bitcoin holdings to the person who collects all the codes" and then vanished once again.

"It's been a year since then. Are there even people who still take that pie-in-the-sky story seriously?"

"That's why it's a good target. Less competition is better, right? Plus, you have a lot of weird knowledge and you love solving mysteries."

"...Let's put that aside for now."

Worried that he might be roped into helping, Mitsuhiro shifted the conversation back and turned his gaze to the luggage Nana was carrying.

"Is this the 'urgent matter that can't tell the reason'?"

"If I didn't say that, you wouldn't take it, would you?"

"Of course not, it's my day off."

Mitsuhiro let out an obvious sigh, having been pushed around by this guy so many times. Ryosuke always easily accepts requests and troubles from his clients, and Mitsuhiro can't completely ignore it since it sometimes leads to actual work, albeit very rarely.

(But... this time, it's clearly a miss.)

Mitsuhiro shot a sharp glare at Ryosuke, who must have realized that, which is why he didn't talk about the reason earlier.

"Why do you always agree to things so easily?"

"When we're in trouble, we help each other out, right?"

"But I'm the one who's always solving the problems."

"Hey! Listen!"

Sensing the increasingly tense atmosphere between them, Nana forcefully stepped in.

"Can we at least hear the story?"

"Ah... yeah, sure."

Mitsuhiro reluctantly agreed to Nana's proposal, but he had a feeling about what was to come from the size and shape of the package she was holding.

Nana opened the package on the table.

"This is..."

As Mitsuhiro expected, it was a painting. With a unique use of colors and a tacky frame, the oil painting seemed to be the work of an 18th-century artist. Nana explained that it had become a hot topic after an influencer mentioned it on social media. With few original pieces available, it was difficult to obtain the artwork even in famous galleries.

"So, you want to insure this painting, right?"

Mitsuhiro interrupted Nana, who was diligently reading a long memo.

"But why Ms. Shiga?"

"The owner was worried about it being stolen, and I was asked to help while we were discussing it..."

Apparently, the painting was forcibly handed over to Nana for "appraisal." Although she hesitated to contact Mitsuhiro directly for such a personal matter, it ended up reaching Ryosuke's ears, and he brought her here. With a wry smile, Mitsuhiro had no choice but to address the situation.

"It would probably be covered under a movable property comprehensive insurance... it might be a one-time payment, though. Is that okay?"

"Is it going to be expensive?"

Mitsuhiro bowed his head in apology to Nana's anxious voice, saying, "Sorry, but I can't help with that. This is a job for an agent, not a head office salesperson like me."

"Didn't you like antiques? Can't you appraise it?"

"It's not my expertise. And the amount of insurance isn't always equal to the painting's price or value."

"I see..."

Disappointed by Nana's reaction, Mitsuhiro felt somewhat guilty, but if Ryosuke had listened properly from the beginning, there would have been no need for any wasted effort. With an internal sigh, Mitsuhiro continued while opening his notebook.

"Well, I know a few specialists, so I'll introduce you to a good insurance agency."

"Thank you very much!"

"As expected of Akutagawa, you're so reliable!"

Sighing for what felt like the umpteenth time today at the cheery tone of his colleagues, Mitsuhiro took a sip of his now lukewarm tea and spoke up.

"Still, it's quite something for someone to go as far as to insure a replica. They must really like the painting."

"Eh?"

Mitsuhiro's comment was met with surprised voices from both Nana and Ryosuke.

"A replica...!?"

"You didn't know?"

"I...I was told it's an original."

Seeing Nana's puzzled expression, Mitsuhiro furrowed his brow.

"Unfortunately, it seems like you've been sold a forgery."

Mitsuhiro's words were merciless.

"In that case, where it was purchased is the problem. I'd like to caution our business partners to avoid getting caught in the same situation, so if possible, could you ask the person to tell you about how they bought it?"

As Mitsuhiro's interest had already shifted elsewhere, Ryosuke stood up from the sofa, unable to hide his confusion.

"Hey, how did you know it wasn't the real deal?"

"Well, I thought it was suspicious because a person who would leave insuring their artwork to someone else probably wouldn't be able to easily obtain such a high-value piece. And, the frame is too old for an 18th-century artist, and the oil paint isn't degraded enough. The lack of even a single crack is unnatural... Whoever made this forgery might not be a professional. Excuse me a moment... Ah, as I thought."

Unaware of Nana's complicated expression at his harsh evaluation, Mitsuhiro tapped the frame with his finger. Ignoring the wide-eyed surprise of his two colleagues, Mitsuhiro flipped the painting over and removed the back of the frame, nodding to himself in understanding.

"This one was made quite recently."

"Recently!?"

With the two of them practically screaming, Mitsuhiro calmly continued his explanation.

"The canvas is brand new, isn't it? Someone probably saw that the painting had become popular and difficult to obtain, and thought they could make a profit by creating a replica... Hm?"

At that moment, as Mitsuhiro was examining the painting closely for any other oddities, he noticed something off.

"Did I just see something...?"

Looking more closely, Mitsuhiro realized that the raised paint in certain areas was catching the light and revealing some sort of shape. Sensing something intentional, Mitsuhiro tilted the painting at various angles, and the mystery presented itself to him with a certain regularity.

"Alphabet...? h...o..."

Mitsuhiro began to write the letters down on paper.

"howdo,youtrust... It's broken up in a strange way, but... How do you trust, maybe?"

"How do you trust?"

It was as if the message was directly questioning Mitsuhiro, and he found himself intrigued by the person who had embedded it.

The translation was almost 100% done by GPT-4, OpenAI’s large-scale language-generation model.

There was a system called "tabs" at that candy store.

The elderly shopkeeper, who had lost confidence in her memory, recorded in a ledger which child bought what on their tab.

One day, a mischievous child secretly changed the ledger, throwing the candy store into chaos.

To prevent this from happening again, the children who wished for peace in the candy store decided to manage the tab information not just by the old lady, but by all the children.

Everyone had a ledger, ensuring that the "same information" existed "simultaneously in multiple copies."

Furthermore, they decided on a rule that when updating the information, at least half of the ledger owners had to verify it first.

This way, even if a mischievous child tried to change the ledger again, the correct information would never be lost.

"――Well, this is a rough idea of how blockchain technology, used in things like Bitcoin, works. There are various mechanisms necessary to make this work, like giving candy to the child who creates a new page in the ledger... Anyway, the advantage is that there's no risk of direct hacking."

Mitsuhiro Akutagawa, who said this, received a serious nod from Nana Shiga in front of him.

"It's great that the kind old lady's store that allows tabs for children is protected...!"

"Yeah... even though it's just a store in an analogy."

"Ah, but I think I 'probably' understood the explanation!"

"I'm glad. So... what I'm curious about is why 'Satoshi Nakamoto' created this system and released it into the world without revealing who they are..."

Mitsuhiro lowered his eyes to the screen of his smartphone and continued as if talking to the person on the other side of the displayed text.

"I feel like there's a big hint in there..."

The opened messaging app showed only the words "Light to the future" in a faint light.

One month earlier――

Calm-colored curtains and rugs, a beautiful wooden table, a soft and carefully selected sofa.

The living room had been carefully arranged for a comfortable day off since Mitsuhiro became a salaryman. Although he no longer had the luxury of being particular about the materials due to certain circumstances, enjoying tea and his favorite classical music in this space was his modest pleasure after days of hard work.

...However.

"...What?"

Speaking with an undisguisedly grumpy tone, Mitsuhiro addressed the man who had suddenly called him.

"Hey, I know it's sudden, but I've got a favor to ask. Right now..."

"I'm on a day off, you know."

As the man tried to explain something, Mitsuhiro hurriedly interrupted him. It couldn't be helped; his coworker, Ryosuke Izumi, always brought up favors that were never good.

"Can't it wait until I go to work tomorrow?"

"I can't explain why, but it's super urgent! So I'm heading over now, okay?"

"Wait, hold on... ah."

Ignoring Mitsuhiro's attempts to refuse, Ryosuke unilaterally rattled off his request and ended the call.

"He never listens to people..."

Although Ryosuke was a troublesome person, it was also Mitsuhiro's fault for not choosing to ignore the call. Giving up on leisurely enjoying his music, Mitsuhiro prepared cups for Ryosuke and whoever he would likely bring along with his "favor."

"...So,"

Mitsuhiro sighed as he faced the two guests sitting on the sofa opposite him.

"Is that the 'urgent matter that can't tell the reason'?"

"I'm sorry! I never thought it would come to this..."

Nana apologized, looking regretful, but Mitsuhiro offered her a resigned smile, saying, "It's not your fault."

As Mitsuhiro had predicted, Ryosuke appeared with a woman by his side. What was unexpected, however, was that she was someone they knew.

"Ms. Shiga?"

"Do you know each other?"

Surprised by their reactions, Ryosuke looked curiously between Mitsuhiro and Nana. The two in question exchanged glances, unsure of how to explain their relationship.

They were not friends, but their relationship was deeper than mere acquaintances. In fact, there was a significant connection to Mitsuhiro's family, but he had no intention of explaining his personal affairs to Ryosuke, who was just a coworker.

"Uh... well, yeah, something like that."

Nana also seemed to sense Mitsuhiro's thoughts and was struggling to figure out how to explain their relationship. However, Ryosuke seemed to have no interest in the matter and simply laughed, saying, "Well, that works out perfectly."

"A guy from my client's sports equipment manufacturer told me there's an employee having trouble with insurance and asked if I could at least hear them out."

"...So why did you bring her to my house?"

"Well, it's best to talk to the person directly when discussing such things, right?"

While Ryosuke's reasoning seemed logical, Mitsuhiro couldn't help but suspect that he just found it too bothersome to handle the matter himself. However, Ryosuke showed no signs of embarrassment and even remarked, "It's a good way to pass the time, isn't it?"

"You're always just lazing around at home on your days off, aren't you?"

"...I'm not exactly lazing around, nor am I just killing time."

"Not killing time? Could it be related to that? Are you searching for that code too?"

"The Code Hunt" refers to the treasure hunt that stirred up the internet a year ago.

It was said that anyone who collected secret words hidden in various locations could amass a vast fortune.

The amount? Approximately 3.2 trillion yen—an amount large enough to host the Olympics.

The organizer, "Satoshi Nakamoto," is the anonymous genius who created the world's first cryptocurrency, Bitcoin.

Satoshi Nakamoto suddenly appeared on the internet, announced cryptocurrency technology, and then disappeared after April 2011.

With their untouched, immensely valuable Bitcoin, over a decade passed. A year ago, Satoshi Nakamoto reappeared on social media.

After actually moving their Bitcoin holdings and proving their authenticity, Satoshi Nakamoto declared, "I will give away all of my Bitcoin holdings to the person who collects all the codes" and then vanished once again.

"It's been a year since then. Are there even people who still take that pie-in-the-sky story seriously?"

"That's why it's a good target. Less competition is better, right? Plus, you have a lot of weird knowledge and you love solving mysteries."

"...Let's put that aside for now."

Worried that he might be roped into helping, Mitsuhiro shifted the conversation back and turned his gaze to the luggage Nana was carrying.

"Is this the 'urgent matter that can't tell the reason'?"

"If I didn't say that, you wouldn't take it, would you?"

"Of course not, it's my day off."

Mitsuhiro let out an obvious sigh, having been pushed around by this guy so many times. Ryosuke always easily accepts requests and troubles from his clients, and Mitsuhiro can't completely ignore it since it sometimes leads to actual work, albeit very rarely.

(But... this time, it's clearly a miss.)

Mitsuhiro shot a sharp glare at Ryosuke, who must have realized that, which is why he didn't talk about the reason earlier.

"Why do you always agree to things so easily?"

"When we're in trouble, we help each other out, right?"

"But I'm the one who's always solving the problems."

"Hey! Listen!"

Sensing the increasingly tense atmosphere between them, Nana forcefully stepped in.

"Can we at least hear the story?"

"Ah... yeah, sure."

Mitsuhiro reluctantly agreed to Nana's proposal, but he had a feeling about what was to come from the size and shape of the package she was holding.

Nana opened the package on the table.

"This is..."

As Mitsuhiro expected, it was a painting. With a unique use of colors and a tacky frame, the oil painting seemed to be the work of an 18th-century artist. Nana explained that it had become a hot topic after an influencer mentioned it on social media. With few original pieces available, it was difficult to obtain the artwork even in famous galleries.

"So, you want to insure this painting, right?"

Mitsuhiro interrupted Nana, who was diligently reading a long memo.

"But why Ms. Shiga?"

"The owner was worried about it being stolen, and I was asked to help while we were discussing it..."

Apparently, the painting was forcibly handed over to Nana for "appraisal." Although she hesitated to contact Mitsuhiro directly for such a personal matter, it ended up reaching Ryosuke's ears, and he brought her here. With a wry smile, Mitsuhiro had no choice but to address the situation.

"It would probably be covered under a movable property comprehensive insurance... it might be a one-time payment, though. Is that okay?"

"Is it going to be expensive?"

Mitsuhiro bowed his head in apology to Nana's anxious voice, saying, "Sorry, but I can't help with that. This is a job for an agent, not a head office salesperson like me."

"Didn't you like antiques? Can't you appraise it?"

"It's not my expertise. And the amount of insurance isn't always equal to the painting's price or value."

"I see..."

Disappointed by Nana's reaction, Mitsuhiro felt somewhat guilty, but if Ryosuke had listened properly from the beginning, there would have been no need for any wasted effort. With an internal sigh, Mitsuhiro continued while opening his notebook.

"Well, I know a few specialists, so I'll introduce you to a good insurance agency."

"Thank you very much!"

"As expected of Akutagawa, you're so reliable!"

Sighing for what felt like the umpteenth time today at the cheery tone of his colleagues, Mitsuhiro took a sip of his now lukewarm tea and spoke up.

"Still, it's quite something for someone to go as far as to insure a replica. They must really like the painting."

"Eh?"

Mitsuhiro's comment was met with surprised voices from both Nana and Ryosuke.

"A replica...!?"

"You didn't know?"

"I...I was told it's an original."

Seeing Nana's puzzled expression, Mitsuhiro furrowed his brow.

"Unfortunately, it seems like you've been sold a forgery."

Mitsuhiro's words were merciless.

"In that case, where it was purchased is the problem. I'd like to caution our business partners to avoid getting caught in the same situation, so if possible, could you ask the person to tell you about how they bought it?"

As Mitsuhiro's interest had already shifted elsewhere, Ryosuke stood up from the sofa, unable to hide his confusion.

"Hey, how did you know it wasn't the real deal?"

"Well, I thought it was suspicious because a person who would leave insuring their artwork to someone else probably wouldn't be able to easily obtain such a high-value piece. And, the frame is too old for an 18th-century artist, and the oil paint isn't degraded enough. The lack of even a single crack is unnatural... Whoever made this forgery might not be a professional. Excuse me a moment... Ah, as I thought."

Unaware of Nana's complicated expression at his harsh evaluation, Mitsuhiro tapped the frame with his finger. Ignoring the wide-eyed surprise of his two colleagues, Mitsuhiro flipped the painting over and removed the back of the frame, nodding to himself in understanding.

"This one was made quite recently."

"Recently!?"

With the two of them practically screaming, Mitsuhiro calmly continued his explanation.

"The canvas is brand new, isn't it? Someone probably saw that the painting had become popular and difficult to obtain, and thought they could make a profit by creating a replica... Hm?"

At that moment, as Mitsuhiro was examining the painting closely for any other oddities, he noticed something off.

"Did I just see something...?"

Looking more closely, Mitsuhiro realized that the raised paint in certain areas was catching the light and revealing some sort of shape. Sensing something intentional, Mitsuhiro tilted the painting at various angles, and the mystery presented itself to him with a certain regularity.

"Alphabet...? h...o..."

Mitsuhiro began to write the letters down on paper.

"howdo,youtrust... It's broken up in a strange way, but... How do you trust, maybe?"

"How do you trust?"

It was as if the message was directly questioning Mitsuhiro, and he found himself intrigued by the person who had embedded it.

The translation was almost 100% done by GPT-4, OpenAI’s large-scale language-generation model.

There was a system called "tabs" at that candy store.

The elderly shopkeeper, who had lost confidence in her memory, recorded in a ledger which child bought what on their tab.

One day, a mischievous child secretly changed the ledger, throwing the candy store into chaos.

To prevent this from happening again, the children who wished for peace in the candy store decided to manage the tab information not just by the old lady, but by all the children.

Everyone had a ledger, ensuring that the "same information" existed "simultaneously in multiple copies."

Furthermore, they decided on a rule that when updating the information, at least half of the ledger owners had to verify it first.

This way, even if a mischievous child tried to change the ledger again, the correct information would never be lost.

"――Well, this is a rough idea of how blockchain technology, used in things like Bitcoin, works. There are various mechanisms necessary to make this work, like giving candy to the child who creates a new page in the ledger... Anyway, the advantage is that there's no risk of direct hacking."

Mitsuhiro Akutagawa, who said this, received a serious nod from Nana Shiga in front of him.

"It's great that the kind old lady's store that allows tabs for children is protected...!"

"Yeah... even though it's just a store in an analogy."

"Ah, but I think I 'probably' understood the explanation!"

"I'm glad. So... what I'm curious about is why 'Satoshi Nakamoto' created this system and released it into the world without revealing who they are..."

Mitsuhiro lowered his eyes to the screen of his smartphone and continued as if talking to the person on the other side of the displayed text.

"I feel like there's a big hint in there..."

The opened messaging app showed only the words "Light to the future" in a faint light.

One month earlier――

Calm-colored curtains and rugs, a beautiful wooden table, a soft and carefully selected sofa.

The living room had been carefully arranged for a comfortable day off since Mitsuhiro became a salaryman. Although he no longer had the luxury of being particular about the materials due to certain circumstances, enjoying tea and his favorite classical music in this space was his modest pleasure after days of hard work.

...However.

"...What?"

Speaking with an undisguisedly grumpy tone, Mitsuhiro addressed the man who had suddenly called him.

"Hey, I know it's sudden, but I've got a favor to ask. Right now..."

"I'm on a day off, you know."

As the man tried to explain something, Mitsuhiro hurriedly interrupted him. It couldn't be helped; his coworker, Ryosuke Izumi, always brought up favors that were never good.

"Can't it wait until I go to work tomorrow?"

"I can't explain why, but it's super urgent! So I'm heading over now, okay?"

"Wait, hold on... ah."

Ignoring Mitsuhiro's attempts to refuse, Ryosuke unilaterally rattled off his request and ended the call.

"He never listens to people..."

Although Ryosuke was a troublesome person, it was also Mitsuhiro's fault for not choosing to ignore the call. Giving up on leisurely enjoying his music, Mitsuhiro prepared cups for Ryosuke and whoever he would likely bring along with his "favor."

"...So,"

Mitsuhiro sighed as he faced the two guests sitting on the sofa opposite him.

"Is that the 'urgent matter that can't tell the reason'?"

"I'm sorry! I never thought it would come to this..."

Nana apologized, looking regretful, but Mitsuhiro offered her a resigned smile, saying, "It's not your fault."

As Mitsuhiro had predicted, Ryosuke appeared with a woman by his side. What was unexpected, however, was that she was someone they knew.

"Ms. Shiga?"

"Do you know each other?"

Surprised by their reactions, Ryosuke looked curiously between Mitsuhiro and Nana. The two in question exchanged glances, unsure of how to explain their relationship.

They were not friends, but their relationship was deeper than mere acquaintances. In fact, there was a significant connection to Mitsuhiro's family, but he had no intention of explaining his personal affairs to Ryosuke, who was just a coworker.

"Uh... well, yeah, something like that."

Nana also seemed to sense Mitsuhiro's thoughts and was struggling to figure out how to explain their relationship. However, Ryosuke seemed to have no interest in the matter and simply laughed, saying, "Well, that works out perfectly."

"A guy from my client's sports equipment manufacturer told me there's an employee having trouble with insurance and asked if I could at least hear them out."

"...So why did you bring her to my house?"

"Well, it's best to talk to the person directly when discussing such things, right?"

While Ryosuke's reasoning seemed logical, Mitsuhiro couldn't help but suspect that he just found it too bothersome to handle the matter himself. However, Ryosuke showed no signs of embarrassment and even remarked, "It's a good way to pass the time, isn't it?"

"You're always just lazing around at home on your days off, aren't you?"

"...I'm not exactly lazing around, nor am I just killing time."

"Not killing time? Could it be related to that? Are you searching for that code too?"

"The Code Hunt" refers to the treasure hunt that stirred up the internet a year ago.

It was said that anyone who collected secret words hidden in various locations could amass a vast fortune.

The amount? Approximately 3.2 trillion yen—an amount large enough to host the Olympics.

The organizer, "Satoshi Nakamoto," is the anonymous genius who created the world's first cryptocurrency, Bitcoin.

Satoshi Nakamoto suddenly appeared on the internet, announced cryptocurrency technology, and then disappeared after April 2011.

With their untouched, immensely valuable Bitcoin, over a decade passed. A year ago, Satoshi Nakamoto reappeared on social media.

After actually moving their Bitcoin holdings and proving their authenticity, Satoshi Nakamoto declared, "I will give away all of my Bitcoin holdings to the person who collects all the codes" and then vanished once again.

"It's been a year since then. Are there even people who still take that pie-in-the-sky story seriously?"

"That's why it's a good target. Less competition is better, right? Plus, you have a lot of weird knowledge and you love solving mysteries."

"...Let's put that aside for now."

Worried that he might be roped into helping, Mitsuhiro shifted the conversation back and turned his gaze to the luggage Nana was carrying.

"Is this the 'urgent matter that can't tell the reason'?"

"If I didn't say that, you wouldn't take it, would you?"

"Of course not, it's my day off."

Mitsuhiro let out an obvious sigh, having been pushed around by this guy so many times. Ryosuke always easily accepts requests and troubles from his clients, and Mitsuhiro can't completely ignore it since it sometimes leads to actual work, albeit very rarely.

(But... this time, it's clearly a miss.)

Mitsuhiro shot a sharp glare at Ryosuke, who must have realized that, which is why he didn't talk about the reason earlier.

"Why do you always agree to things so easily?"

"When we're in trouble, we help each other out, right?"

"But I'm the one who's always solving the problems."

"Hey! Listen!"

Sensing the increasingly tense atmosphere between them, Nana forcefully stepped in.

"Can we at least hear the story?"

"Ah... yeah, sure."

Mitsuhiro reluctantly agreed to Nana's proposal, but he had a feeling about what was to come from the size and shape of the package she was holding.

Nana opened the package on the table.

"This is..."

As Mitsuhiro expected, it was a painting. With a unique use of colors and a tacky frame, the oil painting seemed to be the work of an 18th-century artist. Nana explained that it had become a hot topic after an influencer mentioned it on social media. With few original pieces available, it was difficult to obtain the artwork even in famous galleries.

"So, you want to insure this painting, right?"

Mitsuhiro interrupted Nana, who was diligently reading a long memo.

"But why Ms. Shiga?"

"The owner was worried about it being stolen, and I was asked to help while we were discussing it..."

Apparently, the painting was forcibly handed over to Nana for "appraisal." Although she hesitated to contact Mitsuhiro directly for such a personal matter, it ended up reaching Ryosuke's ears, and he brought her here. With a wry smile, Mitsuhiro had no choice but to address the situation.

"It would probably be covered under a movable property comprehensive insurance... it might be a one-time payment, though. Is that okay?"

"Is it going to be expensive?"

Mitsuhiro bowed his head in apology to Nana's anxious voice, saying, "Sorry, but I can't help with that. This is a job for an agent, not a head office salesperson like me."

"Didn't you like antiques? Can't you appraise it?"

"It's not my expertise. And the amount of insurance isn't always equal to the painting's price or value."

"I see..."

Disappointed by Nana's reaction, Mitsuhiro felt somewhat guilty, but if Ryosuke had listened properly from the beginning, there would have been no need for any wasted effort. With an internal sigh, Mitsuhiro continued while opening his notebook.

"Well, I know a few specialists, so I'll introduce you to a good insurance agency."

"Thank you very much!"

"As expected of Akutagawa, you're so reliable!"

Sighing for what felt like the umpteenth time today at the cheery tone of his colleagues, Mitsuhiro took a sip of his now lukewarm tea and spoke up.

"Still, it's quite something for someone to go as far as to insure a replica. They must really like the painting."

"Eh?"

Mitsuhiro's comment was met with surprised voices from both Nana and Ryosuke.

"A replica...!?"

"You didn't know?"

"I...I was told it's an original."

Seeing Nana's puzzled expression, Mitsuhiro furrowed his brow.

"Unfortunately, it seems like you've been sold a forgery."

Mitsuhiro's words were merciless.

"In that case, where it was purchased is the problem. I'd like to caution our business partners to avoid getting caught in the same situation, so if possible, could you ask the person to tell you about how they bought it?"

As Mitsuhiro's interest had already shifted elsewhere, Ryosuke stood up from the sofa, unable to hide his confusion.

"Hey, how did you know it wasn't the real deal?"

"Well, I thought it was suspicious because a person who would leave insuring their artwork to someone else probably wouldn't be able to easily obtain such a high-value piece. And, the frame is too old for an 18th-century artist, and the oil paint isn't degraded enough. The lack of even a single crack is unnatural... Whoever made this forgery might not be a professional. Excuse me a moment... Ah, as I thought."

Unaware of Nana's complicated expression at his harsh evaluation, Mitsuhiro tapped the frame with his finger. Ignoring the wide-eyed surprise of his two colleagues, Mitsuhiro flipped the painting over and removed the back of the frame, nodding to himself in understanding.

"This one was made quite recently."

"Recently!?"

With the two of them practically screaming, Mitsuhiro calmly continued his explanation.

"The canvas is brand new, isn't it? Someone probably saw that the painting had become popular and difficult to obtain, and thought they could make a profit by creating a replica... Hm?"

At that moment, as Mitsuhiro was examining the painting closely for any other oddities, he noticed something off.

"Did I just see something...?"

Looking more closely, Mitsuhiro realized that the raised paint in certain areas was catching the light and revealing some sort of shape. Sensing something intentional, Mitsuhiro tilted the painting at various angles, and the mystery presented itself to him with a certain regularity.

"Alphabet...? h...o..."

Mitsuhiro began to write the letters down on paper.

"howdo,youtrust... It's broken up in a strange way, but... How do you trust, maybe?"

"How do you trust?"

It was as if the message was directly questioning Mitsuhiro, and he found himself intrigued by the person who had embedded it.

The translation was almost 100% done by GPT-4, OpenAI’s large-scale language-generation model.

There was a system called "tabs" at that candy store.

The elderly shopkeeper, who had lost confidence in her memory, recorded in a ledger which child bought what on their tab.

One day, a mischievous child secretly changed the ledger, throwing the candy store into chaos.

To prevent this from happening again, the children who wished for peace in the candy store decided to manage the tab information not just by the old lady, but by all the children.

Everyone had a ledger, ensuring that the "same information" existed "simultaneously in multiple copies."

Furthermore, they decided on a rule that when updating the information, at least half of the ledger owners had to verify it first.

This way, even if a mischievous child tried to change the ledger again, the correct information would never be lost.

"――Well, this is a rough idea of how blockchain technology, used in things like Bitcoin, works. There are various mechanisms necessary to make this work, like giving candy to the child who creates a new page in the ledger... Anyway, the advantage is that there's no risk of direct hacking."

Mitsuhiro Akutagawa, who said this, received a serious nod from Nana Shiga in front of him.

"It's great that the kind old lady's store that allows tabs for children is protected...!"

"Yeah... even though it's just a store in an analogy."

"Ah, but I think I 'probably' understood the explanation!"

"I'm glad. So... what I'm curious about is why 'Satoshi Nakamoto' created this system and released it into the world without revealing who they are..."

Mitsuhiro lowered his eyes to the screen of his smartphone and continued as if talking to the person on the other side of the displayed text.

"I feel like there's a big hint in there..."

The opened messaging app showed only the words "Light to the future" in a faint light.

One month earlier――

Calm-colored curtains and rugs, a beautiful wooden table, a soft and carefully selected sofa.

The living room had been carefully arranged for a comfortable day off since Mitsuhiro became a salaryman. Although he no longer had the luxury of being particular about the materials due to certain circumstances, enjoying tea and his favorite classical music in this space was his modest pleasure after days of hard work.

...However.

"...What?"

Speaking with an undisguisedly grumpy tone, Mitsuhiro addressed the man who had suddenly called him.

"Hey, I know it's sudden, but I've got a favor to ask. Right now..."

"I'm on a day off, you know."

As the man tried to explain something, Mitsuhiro hurriedly interrupted him. It couldn't be helped; his coworker, Ryosuke Izumi, always brought up favors that were never good.

"Can't it wait until I go to work tomorrow?"

"I can't explain why, but it's super urgent! So I'm heading over now, okay?"

"Wait, hold on... ah."

Ignoring Mitsuhiro's attempts to refuse, Ryosuke unilaterally rattled off his request and ended the call.

"He never listens to people..."

Although Ryosuke was a troublesome person, it was also Mitsuhiro's fault for not choosing to ignore the call. Giving up on leisurely enjoying his music, Mitsuhiro prepared cups for Ryosuke and whoever he would likely bring along with his "favor."

"...So,"

Mitsuhiro sighed as he faced the two guests sitting on the sofa opposite him.

"Is that the 'urgent matter that can't tell the reason'?"

"I'm sorry! I never thought it would come to this..."

Nana apologized, looking regretful, but Mitsuhiro offered her a resigned smile, saying, "It's not your fault."

As Mitsuhiro had predicted, Ryosuke appeared with a woman by his side. What was unexpected, however, was that she was someone they knew.

"Ms. Shiga?"

"Do you know each other?"

Surprised by their reactions, Ryosuke looked curiously between Mitsuhiro and Nana. The two in question exchanged glances, unsure of how to explain their relationship.

They were not friends, but their relationship was deeper than mere acquaintances. In fact, there was a significant connection to Mitsuhiro's family, but he had no intention of explaining his personal affairs to Ryosuke, who was just a coworker.

"Uh... well, yeah, something like that."

Nana also seemed to sense Mitsuhiro's thoughts and was struggling to figure out how to explain their relationship. However, Ryosuke seemed to have no interest in the matter and simply laughed, saying, "Well, that works out perfectly."

"A guy from my client's sports equipment manufacturer told me there's an employee having trouble with insurance and asked if I could at least hear them out."

"...So why did you bring her to my house?"

"Well, it's best to talk to the person directly when discussing such things, right?"

While Ryosuke's reasoning seemed logical, Mitsuhiro couldn't help but suspect that he just found it too bothersome to handle the matter himself. However, Ryosuke showed no signs of embarrassment and even remarked, "It's a good way to pass the time, isn't it?"

"You're always just lazing around at home on your days off, aren't you?"

"...I'm not exactly lazing around, nor am I just killing time."

"Not killing time? Could it be related to that? Are you searching for that code too?"

"The Code Hunt" refers to the treasure hunt that stirred up the internet a year ago.

It was said that anyone who collected secret words hidden in various locations could amass a vast fortune.

The amount? Approximately 3.2 trillion yen—an amount large enough to host the Olympics.

The organizer, "Satoshi Nakamoto," is the anonymous genius who created the world's first cryptocurrency, Bitcoin.

Satoshi Nakamoto suddenly appeared on the internet, announced cryptocurrency technology, and then disappeared after April 2011.

With their untouched, immensely valuable Bitcoin, over a decade passed. A year ago, Satoshi Nakamoto reappeared on social media.

After actually moving their Bitcoin holdings and proving their authenticity, Satoshi Nakamoto declared, "I will give away all of my Bitcoin holdings to the person who collects all the codes" and then vanished once again.

"It's been a year since then. Are there even people who still take that pie-in-the-sky story seriously?"

"That's why it's a good target. Less competition is better, right? Plus, you have a lot of weird knowledge and you love solving mysteries."

"...Let's put that aside for now."

Worried that he might be roped into helping, Mitsuhiro shifted the conversation back and turned his gaze to the luggage Nana was carrying.

"Is this the 'urgent matter that can't tell the reason'?"

"If I didn't say that, you wouldn't take it, would you?"

"Of course not, it's my day off."

Mitsuhiro let out an obvious sigh, having been pushed around by this guy so many times. Ryosuke always easily accepts requests and troubles from his clients, and Mitsuhiro can't completely ignore it since it sometimes leads to actual work, albeit very rarely.

(But... this time, it's clearly a miss.)

Mitsuhiro shot a sharp glare at Ryosuke, who must have realized that, which is why he didn't talk about the reason earlier.

"Why do you always agree to things so easily?"

"When we're in trouble, we help each other out, right?"

"But I'm the one who's always solving the problems."

"Hey! Listen!"

Sensing the increasingly tense atmosphere between them, Nana forcefully stepped in.

"Can we at least hear the story?"

"Ah... yeah, sure."

Mitsuhiro reluctantly agreed to Nana's proposal, but he had a feeling about what was to come from the size and shape of the package she was holding.

Nana opened the package on the table.

"This is..."

As Mitsuhiro expected, it was a painting. With a unique use of colors and a tacky frame, the oil painting seemed to be the work of an 18th-century artist. Nana explained that it had become a hot topic after an influencer mentioned it on social media. With few original pieces available, it was difficult to obtain the artwork even in famous galleries.

"So, you want to insure this painting, right?"

Mitsuhiro interrupted Nana, who was diligently reading a long memo.

"But why Ms. Shiga?"

"The owner was worried about it being stolen, and I was asked to help while we were discussing it..."

Apparently, the painting was forcibly handed over to Nana for "appraisal." Although she hesitated to contact Mitsuhiro directly for such a personal matter, it ended up reaching Ryosuke's ears, and he brought her here. With a wry smile, Mitsuhiro had no choice but to address the situation.

"It would probably be covered under a movable property comprehensive insurance... it might be a one-time payment, though. Is that okay?"

"Is it going to be expensive?"

Mitsuhiro bowed his head in apology to Nana's anxious voice, saying, "Sorry, but I can't help with that. This is a job for an agent, not a head office salesperson like me."

"Didn't you like antiques? Can't you appraise it?"

"It's not my expertise. And the amount of insurance isn't always equal to the painting's price or value."

"I see..."

Disappointed by Nana's reaction, Mitsuhiro felt somewhat guilty, but if Ryosuke had listened properly from the beginning, there would have been no need for any wasted effort. With an internal sigh, Mitsuhiro continued while opening his notebook.

"Well, I know a few specialists, so I'll introduce you to a good insurance agency."

"Thank you very much!"

"As expected of Akutagawa, you're so reliable!"

Sighing for what felt like the umpteenth time today at the cheery tone of his colleagues, Mitsuhiro took a sip of his now lukewarm tea and spoke up.

"Still, it's quite something for someone to go as far as to insure a replica. They must really like the painting."

"Eh?"

Mitsuhiro's comment was met with surprised voices from both Nana and Ryosuke.

"A replica...!?"

"You didn't know?"

"I...I was told it's an original."

Seeing Nana's puzzled expression, Mitsuhiro furrowed his brow.

"Unfortunately, it seems like you've been sold a forgery."

Mitsuhiro's words were merciless.

"In that case, where it was purchased is the problem. I'd like to caution our business partners to avoid getting caught in the same situation, so if possible, could you ask the person to tell you about how they bought it?"

As Mitsuhiro's interest had already shifted elsewhere, Ryosuke stood up from the sofa, unable to hide his confusion.

"Hey, how did you know it wasn't the real deal?"

"Well, I thought it was suspicious because a person who would leave insuring their artwork to someone else probably wouldn't be able to easily obtain such a high-value piece. And, the frame is too old for an 18th-century artist, and the oil paint isn't degraded enough. The lack of even a single crack is unnatural... Whoever made this forgery might not be a professional. Excuse me a moment... Ah, as I thought."

Unaware of Nana's complicated expression at his harsh evaluation, Mitsuhiro tapped the frame with his finger. Ignoring the wide-eyed surprise of his two colleagues, Mitsuhiro flipped the painting over and removed the back of the frame, nodding to himself in understanding.

"This one was made quite recently."

"Recently!?"

With the two of them practically screaming, Mitsuhiro calmly continued his explanation.

"The canvas is brand new, isn't it? Someone probably saw that the painting had become popular and difficult to obtain, and thought they could make a profit by creating a replica... Hm?"

At that moment, as Mitsuhiro was examining the painting closely for any other oddities, he noticed something off.

"Did I just see something...?"

Looking more closely, Mitsuhiro realized that the raised paint in certain areas was catching the light and revealing some sort of shape. Sensing something intentional, Mitsuhiro tilted the painting at various angles, and the mystery presented itself to him with a certain regularity.

"Alphabet...? h...o..."

Mitsuhiro began to write the letters down on paper.

"howdo,youtrust... It's broken up in a strange way, but... How do you trust, maybe?"

"How do you trust?"

It was as if the message was directly questioning Mitsuhiro, and he found himself intrigued by the person who had embedded it.

The translation was almost 100% done by GPT-4, OpenAI’s large-scale language-generation model.