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Past - Gen POV
Gen runs from one side of the room to the other, writing here, rearranging things there, sticking notes to every available surface, checking and rechecking everything.
Tomorrow is his seventeenth birthday, which means that, if the conditions line up just right, when he wakes up, he might no longer be in his own bed—or even in his own house, for that matter. Hell, he might not even be in the same city.
Because he will have switched bodies with his soulmate.
One of the most important events in every teenager’s life—alongside first love, getting a driver’s license, puberty, and so on—was the body swap. Since time immemorial, most people had experienced this phenomenon twice in their lives: once on each soulmate’s seventeenth birthday.
Of course, there were cases in which it never happened. For example, when one half of the pair died prematurely. There were also cases in which the switch happened earlier than expected, such as when one person inevitably turned seventeen before the other. There had even been records of stranger cases involving more than two people switching bodies, although only a small handful had ever been documented in centuries of research.
The cultural and symbolic meaning of the exchange had evolved throughout history, but if there was one thing people had always agreed on, it was that those involved were permanently connected by something intangible, something unbreakable, something irreplaceable. What exactly that connection meant, however, was something the people involved had to decide for themselves.
Either way, it was a day worth celebrating.
The first switch marked an important milestone in the transition from childhood to adulthood, while the second one served to cement it. The exchange had to happen twice to complete the cycle. Depending on who you asked, it could be interpreted as a process of coming to know both yourself and the other person at different stages of maturity: the first occurring while one half was still too young to consciously remember the experience, and the second taking place once both had reached maturity, allowing them to finally retain a complete memory of it.
Whatever the explanation, Gen’s day would be tomorrow.
It would be his first switch, which made it pretty clear that he was the older of the two—because nobody liked to entertain the possibility that the other half simply didn’t exist. It also meant he supposedly wouldn’t remember much once he returned to his own body, at least not until the second exchange.
Spending an entire day inside a stranger’s body was terrifying enough as it was, especially if you weren’t prepared for it beforehand. So before going to sleep, Gen prepares his entire room for his soulmate’s arrival, determined to make sure they don’t panic.
He sets his phone to unlock with his fingerprint, lays out clothes for the following day, takes a shower so his other half won’t have to, and clears his schedule of any obligations. Anything to make sure that whoever woke up in his body the next morning could enjoy a quiet, peaceful day in his life.
His parents watch him in silence, their expressions equal parts curious and amused. Their own switch had been so easy it almost felt like cheating. Having known each other since childhood and seeing each other literally every damn day, no one had been particularly surprised when, on Stanley’s seventeenth birthday, his soulmate turned out to be Xeno.
Which meant neither of them had ever had to face the kind of teenage crisis their son was going through on the night before the most important day of his short life.
Gen checks everything three times. He adds notes in English, Spanish, French, and Japanese—with his father’s help, just in case there happens to be a communication problem—and says goodnight to his parents at exactly midnight.
It is now his seventeenth birthday.
He lies down on his bed, turns off the bedside lamp, and closes his eyes, waiting expectantly to switch places with his other half.
Past — Gen POV
When he woke up, it felt as though he hadn’t slept at all.
He turned over, hoping to get a little more sleep before the alarm went off, but no matter how he positioned himself, the sunlight streaming through the window refused to leave him alone.
That was when he noticed.
He lifted his head from between the pillows so quickly that the body he was currently inhabiting would definitely feel the consequences tomorrow.
Which was fine.
He wouldn’t be there when that happened.
His eyes swept across the room, and he immediately noticed that not only was there no alarm clock, but there wasn’t even a bedside table.
The room, illuminated by the late-morning sunlight, was filled with strange machines, wires, books, and the occasional Doraemon poster.
His breath caught in his chest as he took in the sight.
This was his other half’s bedroom.
Slowly, he sat up, finding it strange that his hair didn’t fall over one side of his face. Instead, there was only a single strand hanging in front of him.
His hair was not only white now, but the tips faded into a peculiar shade of green.
He slowly held his hands out in front of him, getting used to the unfamiliar body. What he had initially assumed was simply short hair actually extended in a way that seemed almost unnaturally long.
Curious.
His counterpart’s phone began ringing again, most likely what had woken him up in the first place. He recognized the writing system as Japanese, but he wasn’t quite advanced enough to read it without help.
Shit. I should’ve studied harder.
Still, he answered, relying on his pathetic attempt at fumbling through Japanese to say what he remembered was the proper way to greet someone and introduce himself.
On the other end, the voice immediately grew louder, forcing him to pull the phone away from his ear.
He had never imagined that someone on the other side of the world could possess such impressive lungs.
Panicking, he hung up.
He dropped the device onto the mattress in horror, unsure whether he had just done something terribly wrong. His hand itched instinctively to grab his own phone and look for a translator, but his phone was no longer within reach. The only device he had was this one—the one belonging to his spiritual counterpart.
He tiptoed around the room, terrified of accidentally touching something and breaking something priceless—a lesson learned after years of disastrous experiences involving sneaking into his father’s laboratory without supervision—before inevitably making his way to the bathroom.
He took a deep breath, did what he had to do purely on muscle memory, and avoided looking any more than necessary before getting dressed again.
After that, he explored the small apartment.
Apparently, his counterpart lived alone despite being underage, which was curious, to say the least. Not knowing what he could touch or where he was supposed to look, he simply put some water on to heat, hoping he might at least be able to make himself a cup of tea.
After getting changed, he could take the time to snoop around and explore the place more thoroughly.
For now, it was enough to know where the bathroom, kitchen, and bedroom were.
There was no loose-leaf tea or tea bags on the kitchen counter, but he did find instant coffee, which he figured would do for the moment. His body, apparently accustomed to terrible eating habits, practically begged him for a strong cup of coffee—the kind he had never actually liked.
So, anyway, he made it.
And drank it.
He was surprised by how differently his sense of taste worked.
When he was halfway through the cup, someone knocked on the door.
Still moving on tiptoe, he approached and cautiously opened it, still wearing his pajamas.
Outside stood two teenagers around his age—a boy and a girl—both looking as though they had just run a marathon. They stood in what appeared to be an open-air apartment corridor, trying desperately to catch their breath.
Well.
His brain had better start remembering those Japanese lessons, because apparently, today was the day of his trial by fire.
Past — Senku POV
When Senku opens his eyes, he realizes he has lost count of the seconds he had been keeping track of in the back of his mind—an experiment to test the limits of his own neural capacity.
The second thing he notices is that there are no rays of sunlight streaming through any window above his head.
There are windows.
They’re just nowhere near where they should be.
He sits up abruptly, feeling strange in a way that would be difficult to describe without sounding like a complete lunatic. In any case, it feels as though his skin is too loose, or his bones are somehow too heavy. Everything inside him feels wrong, as if things aren’t where they’re supposed to be.
He jumps out of bed, getting one foot tangled in the blankets and sending everything crashing to the floor in the process.
But that’s the least of his concerns.
He runs off in search of a mirror.
He is already completely certain of what is happening, but he needs to see it with his own eyes to confirm it.
There, staring back at him from the mirror, is a freshly seventeen-year-old boy with long black hair falling to his shoulders and narrow eyes.
“Well, would you look at that,” he says, his eyes widening at the sound of that body speaking in his native language. “Isn’t that interesting?”
Whoever his other half was, they had left everything perfectly arranged so he wouldn’t have to worry about a thing. He finds notes scattered throughout the room in four different languages, telling him where to find the clothes that had already been laid out for him, along with several other pieces of rather important information.
There is already movement coming from somewhere else in the house, which means he isn’t alone. So he makes himself look as presentable as possible with the clothes provided and heads out to introduce himself.
Two middle-aged men look up and watch him approach in silence, each holding a cup of coffee and that morning’s newspaper. They are having breakfast quietly, scrutinizing him as though trying to determine whether whoever currently inhabits their son’s body is worthy of being there.
He won’t admit that he swallowed when he finally stopped at the end of the dining table.
But the truth is, he came pretty close.
“I assume you’re not Gen?”
The man with white hair and belt buckles worn like chokers asks the question in English.
Senku wants to answer no, but every bit of English knowledge he possesses—and his seven-hundred-day Duolingo streak—promptly flies out the window.
He could simply shake his head.
But something tells him the bloodthirsty-looking blond man wouldn’t consider that an acceptable answer.
“My name is Senku Ishigami,” he says, his pronunciation correct but carrying an accent that always sounds strange next to a native speaker.
“Ah, a Japanese boy! Isn’t that classy, Stan?”
The white-haired man seems delighted in a rather peculiar way, wearing an expression that suggests he understands far more than he should. He slaps the blond man beside him on the shoulder as if this were the best day of his life.
Back in the bedroom, Gen had left a single note that hadn’t been translated into four different languages. Senku assumes it had been written at the last minute.
It specifically warned him about this situation.
About Gen’s parents.
According to the note, they would probably try to intimidate him because they fed on other people’s discomfort at breakfast, apparently absorbing enough energy to last them through the rest of the day as if awkwardness were some kind of protein bar.
But, despite that, they weren’t bad people.
Weird?
Yes.
Gothic?
Also yes.
But not bad.
The blond man lowers the cup he has been drinking from, leaving a mark of lipstick on the porcelain as dark as his soul.
“I hope you can manage speaking English, because unlike my husband, I don’t speak anything else.”
He gestures with his head toward the white-haired man, who smiles even wider.
It is less of a Nice to meet you smile and more of a I hereby commence this autopsy kind of smile.
For a moment, Senku considers going back to sleep until tomorrow.
But he also knows this is something he will have to deal with sooner or later. These people, no matter how unusual they might be, are his other half’s parents. One way or another, he will have to get through them first.
Feeling protected by the simple fact that he is still inside his soulmate’s body—and reasonably certain that neither of these people would be capable of harming their own son—he answers with a slightly smug smile.
“I can manage well enough.”
The blond rolls his eyes and leaves his husband to take over, having apparently failed to intimidate the new brat.
The white-haired man, who is apparently the one in charge of this relationship, picks up the baton with an enthusiasm that seems deeply unhealthy.
“Then, Mr. Senku,” he says, switching unexpectedly into remarkably fluent Japanese, “my name is Xeno Houston Wingfield, my husband over here is Stanley Snyder, and you, for better or worse, are currently in the body of our son, Gen.”
That single sentence contains a finite amount of information, and Senku’s brain immediately sorts it from most important to least important with perfect efficiency.
Among the information categorized as Important, two things battle for his attention.
His other half’s name is Gen.
And his father is, out of all people, literally his mentor.
His eyes widen almost comically for a fraction of a second before he manages to regain control of his expression, disguising his surprise by pressing the shell of his ear with the tip of his pinky finger.
Xeno’s smile widens even further, noticing his student’s surprise with obvious delight.
Beside him, Stanley rises from his seat at the head of the table, kisses Xeno on the forehead like a devoted husband, stares intently at his supposed son while casually slinging a fucking shotgun over his shoulder, and walks out the door as though this were any other ordinary day at work.
“Well then, Dr. Senku,” Xeno says.
“How would you like to accompany me to NASA today?”
Past- Gen POV
Yuzuriha—God bless her—seems to be the only one who came prepared for a situation like this.
She pulls out her phone from her backpack—because apparently, the two of them had skipped class to come find him—and downloads a real-time conversation translator. Once that problem is solved, she leaves him alone with Taiju, who appears to be his other half’s best friend, and runs into Senku’s bedroom to find him something to wear for the day.
Once he’s dressed and thoroughly not combed—because they informed him that this is, in fact, what his hair normally looks like—he sits down to have breakfast with his guests.
Taiju continues talking at the top of his lungs, but he’s no longer as intimidating as he had been at first. Meanwhile, Yuzuriha makes pancakes and speaks patiently, trying to give the translation app enough time to interpret her words correctly.
Apparently, he is in Tokyo, inhabiting the body of someone named Ishigami Senku.
His soulmate seems to be a fifteen-year-old scientist with a love for ramen and Doraemon, whose father is currently in the United States—more specifically, at NASA—preparing for his next launch into space.
Well.
The world has this peculiar habit of being far too small sometimes.
There are several hours of difference between his home and his other half’s, but he imagines Senku must be having a great time over there with his parents.
Taiju and Yuzuriha, having completely abandoned any intention of returning to class, begin planning out the rest of their day. He’s in one of the largest metropolises in the world, after all, so he might as well take advantage of the opportunity to do some sightseeing.
Even if he’s inevitably going to forget all of it the next day.
He unlocks Senku’s phone, which fortunately only requires his fingerprint, and asks for help changing the device’s default language from Japanese to English for his own convenience.
The wallpaper shows himself—or rather, Senku—sitting with Taiju and who appears to be his father, eating ramen.
He stares at the picture for a moment too long before the screen inevitably goes dark, wishing with all his heart that he could somehow burn the image into his retinas.
Senku keeps a detailed record of all his daily activities, but Gen can’t make much sense of it with his limited Japanese. So, with a silent apology for ignoring whatever plans Senku had made for the day, he decides to make it up to him by writing a detailed record of everything he does instead.
Maybe someday, when they inevitably cross paths, he’ll be able to look back through his notes and remember everything he is about to forget.
He has spent the entire morning trying to build a profile of his soulmate, who seems to be just as peculiar as he is interesting.
If he thinks about it, it makes perfect sense that this person would be his other half.
He walks in his footsteps. Experiences the things he would experience in his day-to-day life. Sees his surroundings through his eyes.
The ease with which he adapts to this out-of-body experience terrifies and excites him in equal measure, but he decides to push those feelings aside as he walks through the streets of Asakusa for the first time.
Kaminarimon, with its enormous red lantern, welcomes him with open arms and brilliant colors.
The crowded streets of Nakamise-dori swallow them up between food stalls and little souvenir shops, making his mouth water in a way he never imagined so many unfamiliar smells could.
This body reacts to certain stimuli in unexpected ways. It seems far more drawn to spicy aromas, high-pitched voices, and sharp, sudden sounds.
Taiju laughs at every reaction, keeping a hand on his shoulder so they don’t lose each other in the crowd.
Yuzuriha takes pictures—not very discreetly—and seems overwhelmingly happy to spend the day showing her city to a stranger inhabiting her friend’s body.
They both insist that if he needs anything, anything at all, he can count on them to get it. The same goes for any temple or exhibition he might want to visit that requires an entrance fee.
But Gen doesn’t feel comfortable spending someone else’s money without giving them anything in return.
Noon arrives in the blink of an eye.
By then, his stomach has been growling intermittently every fifteen minutes, and he has been hoping that the noise of the crowd around him is loud enough to hide it.
Apparently, judging by the way Yuzuriha is looking at him, it isn’t.
The couple guides him toward a row of vending machines.
Energy drinks and Coca-Cola are stacked in perfect harmony, but to his surprise, it isn’t his favorite drink that makes his mouth water.
Beside him, Yuzuriha fiddles with her phone for a moment before raising it to her ear and launching into Japanese so quickly that he can barely understand any of it.
A moment later, she holds the device out to him as if expecting him to speak too.
Gen turns his head from side to side, as though he must have misunderstood.
Yuzuriha simply shakes the phone at him more insistently, forcing him to answer with nothing more than a look.
A number glows on the screen.
One he doesn’t recognize.
But it has his hometown’s area code.
He takes the phone carefully, unsure of what to expect.
“Hello?” he asks, his English hesitant in a way that feels entirely unlike him.
“Gen!”
The person on the other end sounds like an older man.
“It’s so nice to meet you! Thank you for being in my son’s body!”
Thank you?
“N-Nice to meet you, sir,” he says in English, stunned by the realization that he may very well be speaking to his future father-in-law.
“Don’t call me ‘sir.’ Call me Byakuya. Bya-ku-ya.”
The person on the other end enunciates the syllables cheerfully, as though he has been waiting for this day his entire life.
“Or you can call me Dad if you want!”
And then he laughs as if that is a perfectly normal thing to say.
Gen imagines the looks of absolute disgust his parents would make, and the thought is far too amusing.
Still, he decides to start off on the right foot and maintain some boundaries.
For now.
“Byakuya,” he decides, already recognizing the name from some of his favorite anime characters.
“Yuzuriha told me about the situation. Do you need money?”
Gen immediately begins trying to refuse in a panic, mortified by the question, but he is interrupted before he can get the words out.
“Senku has savings for emergencies that don’t involve accidents in the lab, which is exactly what this is. You’re free to use them however you want, so don’t worry about it. Taiju and Yuzuriha will help you with anything else, so you can relax.”
Gen shoots Yuzuriha a furious look.
She only gives him a thumbs-up and a conspiratorial smile.
“Regardless of the situation,” Byakuya continues through the speaker, “you’re in my son’s body. It would put my mind at ease if you at least ate properly for the rest of the day.”
And Gen can’t really argue with that logic.
He promises to take responsible care of Senku’s body for the remainder of the day, even if that means spending some of his savings on basic expenses.
On the phone, Byakuya keeps talking in excited, though occasionally halting, English. He tells Gen over and over how happy he is to finally meet him and how much he hopes they will be able to meet in person someday.
It leaves Gen with a strange mixture of sadness at the thought of everything he is about to forget and anticipation for whatever the future might bring.
Taiju finishes the can of soda he bought earlier and chats quietly with Yuzuriha.
Gen knows he should end the call soon.
But part of him doesn’t want to.
Before hanging up, one final thought crosses his mind like lightning, and he feels compelled to try his luck.
“The others mentioned that you work at NASA…”
He pauses, waiting for the man on the other end to confirm before continuing.
“By any chance, do you know someone named Dr. Xeno?”
The other end of the line falls into stunned silence for what feels like five entire seconds before suddenly coming back to life.
“Yes?” Byakuya asks, sounding confused. “Why do you ask?”
Gen, inside Senku’s body, swallows nervously.
“If you see him… could you tell him I’m okay?”
Byakuya audibly takes a breath on the other end of the line, clearly seconds away from unleashing the kind of scream that would tear his lungs apart at the horrifying realization that he is speaking to Xeno’s son.
Gen sees what is coming.
Panics.
And hangs up before it can happen.
Taiju and Yuzuriha emerge from their own little bubble and look at him with identical smiles.
They still have all of Tokyo left to explore.
Plenty of things to do.
And an entire day ahead of them.
How exciting!
Past — Senku POV
If he had to choose between the Xeno from the emails and the Xeno in the flesh, he would definitely go with the one from the emails.
Nevertheless, you don’t get invited to NASA just any old day, so he ignores the constant passive-aggressive remarks about destroying society and ruling over its remaining scraps with an iron fist and focuses instead on enjoying everything the facilities have to offer.
He slips into one of the spare white lab coats Xeno offers him, and within minutes, he’s just another scientist—provided you ignore the very obvious lanyard hanging around his neck with a visitor badge attached to it.
Xeno enjoys parading him from one place to another like a trophy son, his flesh and blood, his greatest pride. Senku, thoroughly amused by the situation, lets himself be dragged around without complaint, enjoying the opportunity to meet people, make connections, and explore parts of NASA normally outside civilian limits.
In any case, it means he’s already won over one of his future fathers-in-law, which is more than half the work done.
Now all he has to do is win over the one with the shotgun.
He’ll have time to plan that roadmap in the future.
Gen’s unruly strands, long enough to get in the way but too short to tie back, keep falling from behind his ears as he looks through telescopes and reads reports, forcing him to familiarize himself with his new body in more intimate ways.
For example, after today, he thinks he could recognize his soulmate’s straight, silky hair by touch anywhere.
The truth is, he has never felt particularly attracted to anyone, nor has he ever been interested in figuring out what that might mean.
What he has felt is curiosity about what his counterpart would look like.
Much to his surprise, he isn’t ugly in the slightest.
Curious eyes framed by narrow eyelids, a slightly upturned nose, soft lips, elegant features.
The fact that he spent about twenty minutes that morning staring at himself in the bathroom mirror is nobody’s business but his own.
He has a typical American lunch, packed with calories and lacking in nutrients, the kind of meal that under any other circumstances might give him a liver attack, but that this body handles as though it were nothing.
Then comes the irresistible craving for a Coca-Cola—a drink he has never actually liked all that much.
Curious to experience everything this unfamiliar body has to offer, he samples everything to his heart’s content, comparing tastes and smells against his usual records.
Xeno watches everything with genuine curiosity, taking notes, asking questions, and comparing the information with what he has learned from raising a child nearly to adulthood.
When it came to tastes and preferences, he and Stanley had never really differed on anything, so experiencing the senses of someone from such a close perspective is an opportunity too interesting to ignore.
Time slips through their fingers like water.
Gen’s body grows tired and sleepy, apparently accustomed to taking naps after lunch. Senku, unwilling to waste his day sleeping, forces himself to stay awake despite the headache it gives him.
His reward?
A reprimand from Xeno in the form of a flick to the forehead.
One might imagine that hooking your index and middle fingers beneath your thumb to build up tension before letting them snap forward shouldn’t hurt.
Wrong.
Xeno is just as skilled at that as he is at building rockets, and Gen’s body seems sufficiently accustomed to the punishment that it instinctively braces itself, shrinking away just before impact despite Senku having no conscious intention of doing so.
The scientist raises an eyebrow, intrigued by the familiar reaction Gen usually has when receiving his reprimand—but this time orchestrated by the person inhabiting his son’s body.
Senku merely shrugs, rubbing his forehead with an annoyed expression.
Xeno, being the good father that he is, insists that an hour-long nap won’t kill him and sends him off to sleep in the break room, offering to push a few chairs together like he used to when Gen was a child.
It isn’t the first time Gen has taken a nap at NASA, and it probably won’t be the last, so there shouldn’t be any problem.
Senku stubbornly protests, which does nothing but worsen his headache and earn him another flick to the forehead.
Faced with the terrifying prospect of remaining on the receiving end of that particular punishment for the rest of the day, he eventually gives in to his mentor’s not-so-gentle suggestion.
They head to the break room, where Senku stretches himself out across a comfortable-looking couch and lets sleep begin to overtake him.
He thinks he hears vague whispers somewhere outside the room, but he is so tired that he can’t quite make out what they’re saying.
Leaning against the doorframe, Byakuya and Xeno watch him fall asleep like a child, their expressions softening into something only years of parenthood could have unlocked.
They exchange a few quiet words, careful not to disturb the sleep of the boy who is, for the moment, both of their sons.
Then they bid each other farewell with a nod.
Just before turning the corner down the hallway, Byakuya turns back one last time, a grin spreading from ear to ear.
“Oh, right. Gen asked me to tell you he’s okay.”
Xeno blinks a couple of times.
Then he lets out the breath he hadn’t realized he was holding, snorts, rolls his eyes, and turns back to his own work.
Leaving Senku to sleep in peace.
Present — Gen POV
Fate turns out to be cruel enough to allow him only a single switch; an incomplete one, of which he remembers almost nothing, even less so after thousands of years spent petrified.
The only thing he knows is that, after waking up in his own body again, he developed an urgent need to start specializing in Japanese and even traveled to the Land of the Rising Sun several times.
He isn’t sure whether it has anything to do with the switch, but he has never been a fan of ignoring his instincts, so he throws himself headfirst into his newfound interest.
His hair is still dyed with religious devotion, but now he leaves only one side long, figuring that, if he has to deal with it, it might as well be only half as annoying.
His parents enthusiastically approve of his new style, emphasizing the importance of distinguishing oneself from the rest of the unworthy mortals.
In their dictionary, that translates to: “It looks cute on you.”
He carefully keeps the sheet of paper on which his soulmate wrote, in handwriting that is somehow partly his and partly foreign to him, everything he experienced during the twenty-four hours he spent occupying Gen’s body.
However, the day when he expects the next switch to happen—this time with more permanent memories—never comes.
Humanity is petrified from one moment to the next, taking with it what little remained of that experience, including that single sheet of paper.
Petrification catches him completely off guard in Japan, terribly far away from his parents and the protection they provide.
The Stone Age imposes itself overwhelmingly upon everything and everyone, including him, and the scattered remains of statues everywhere make him imagine the most unfortunate scenarios for the people he loves.
And, as if that weren’t enough, he ends up living under the rule of a muscular dictator with an iron fist and a murderous tendency toward anyone who practices science—God forbid he discovers that Gen is the firstborn son of one of them.
Setting that aside, he adapts fairly well to the rules and customs of the Tsukasa Empire.
Although he wakes up exactly as he came into the world, clothing turns out not to be the problem he imagined it would be.
The girl who provides his clothes looks painfully familiar, but he never manages to figure out why, because he is certain he has never met her before.
The giant who follows her around like a shadow also strikes him as a nostalgic sight, as though seeing the two of them together is somehow unquestionably right.
He doesn’t know why, but his mind seems to understand and follow the couple’s habits as though he has experienced them before.
If they find it strange, they don’t comment on it. They simply smile, their sad expressions fitting for their current situation as hostages, which only makes the dangerous and inexplicable affection he develops for them happen all the faster.
He hopes to finish quickly, either confirming or denying the death of whatever poor bastard had the misfortune of crossing paths with Tsukasa, and then run back to Taiju and Yuzuriha—the only two faces that truly feel familiar throughout this entire nightmare.
He thinks about his soulmate, wondering whether he is still in one piece.
Hopefully, he hasn’t woken up yet.
Not with that lunatic running around.
Why wouldn’t he want Senku to run into Tsukasa?
It is then that his kind, yet deeply disturbed dictator leads him to the tree where it all began.
The place where the first Homo sapiens sapiens of the old world walked once again across this new land and built miracles with his bare hands as though he were some kind of new messiah.
“That’s why I had to eliminate him,” Tsukasa explains, paying little attention to the look of astonishment spreading across Gen’s face.
There, the same man who is reviving ancient dreams in modern lands wrote down the date on which he emerged from the stone, as though counting for 3,700 years were nothing more than a children’s game.
That date, now serving as a natural aggravating factor in Gen’s already complicated moral situation, is his fucking birthday.
Gen, who has always been painfully romantic and enthusiastic about looking for signs of destiny where sometimes there aren’t any, knows perfectly well that this has to be some kind of sign.
The problem is that he has no idea what it means.
If the date carved into that tree is what he thinks it is, sooner or later he will have to venture into the depths of untouched wilderness in search of humanity’s last first scientist.
Alive or not.
Well, he thinks, he’d better be alive, because I’m not planning on spending the rest of my life alone.
Ishigami Village is characterized by having an alarmingly high average of impulsive idiots per capita.
At the center of them all, the miracle worker bustles around in an endearing manner, mixing things here and moving things there.
Working tirelessly to overcome Tsukasa’s philosophy with nothing but science.
He thinks about Taiju and Yuzuriha, prisoners in the Empire of Might, waiting for him to return.
But then he sees Senku, creating light from absolutely nothing, and he knows he has chosen a side—perhaps long before he was even reborn.
He may or may not be certain that Senku is who he thinks he is, but he has nothing to lose by finding out.
Senku clearly seems to be someone very dear to his imprisoned friends, and Gen really doesn’t want to keep seeing their miserable faces every time he returns from a mission.
Life in the Kingdom of Science, unlike life in the Empire of Might, is laborious and, contrary to popular belief, not actually hard.
He doesn’t go hungry or cold—not like the people still stuck on the other side—but it is exhausting in the most literal sense of the word.
Still, he takes advantage of the closeness Senku seems to feel toward him as motivation to discover whether he really is the person Gen believes him to be.
One of the greatest lessons his parents ever taught him was to look at the glass as half full, regardless of the situation.
He chooses to imagine a simple glass filled halfway with water, setting aside his parents’ preferred interpretation of a glass half-filled with blood, oil, or whatever murky liquid happened to be available.
He never says anything about his suspicions.
That would be counterproductive, in Senku’s own words.
Senku has never confirmed or denied having experienced the first switch, but he somehow manages to get the exact amount of sweetness Gen likes in his Coca-Cola on the very first try.
Gen has plenty of evidence and very few doubts.
But accumulating that evidence takes time.
So it isn’t until around New Year’s that he casually slips the question of Senku’s birthday into the metaphorical conversation, waiting for his scientific leader to pick it up without giving it much thought.
Imagine his face when he discovers that it is none other than the date opposite his own birthday—the exact same date carved so long ago into a tree near the Miracle Cave.
However, that reveals something much more urgent.
Senku will turn seventeen in only a few days, right in the middle of building the cell phone.
A quick consultation with Ruri reveals details about the switches described in the Hundred Stories, but not everyone in Ishigami Village has experienced one, so there isn’t much information available about what to do in cases like theirs.
Which leaves Gen right back where he started:
Having absolutely no idea how to prepare for the switch.
Senku, completely unaware that he will most likely be switching bodies in only a few days, simply keeps working as though nothing is happening, leaving the rest of his friends completely in the dark about his birthday.
And that is precisely why Gen comes up with the most ambitious plan of his short life:
Building an observatory.
On the morning of the first day of the new year, Senku heads toward the far reaches of the rock in search of tungsten for the vacuum tubes, accompanied by Chrome and Magma.
Each of them receives their respective instructions for what to do three days from now, when they are due to return from their expedition.
Once they disappear over the horizon, Gen gets to work.
The rest of the villagers cling to him like some kind of duckling imprinting on its mother, which ultimately works in his favor when it comes to handling the heavy lifting.
He has a very close deadline and a hell of a lot of work to do.
So he gets to it.
Whether Senku is his soulmate or not, Gen is going to finish this gift on time and in perfect condition, even if it is the last thing he ever does.
Present — Gen POV
When he opens his eyes that morning, his body feels unbearably heavy, as though he had been submerged in ice-cold water for hours.
He doesn’t remember staying up so late going over the observatory blueprints, but there’s a good chance he caught a chill and is finally coming down with something in this Stone World.
Beside him, Chrome snores through what sounds suspiciously like sleep apnea, something he’ll have to check once they manage to revive an otolaryngologist. Other than that, the rest of the cave is silent.
Cave? Silence?
He shoots upright in his sleeping bag, immediately regretting it when his aching body protests.
Goddammit.
Of course his second switch—the one he was actually supposed to remember—had to happen under circumstances like these.
The observatory still needs its final details finished, which he is certain will be left in Senku’s hands, now that his soulmate has been officially confirmed, until he returns to the village.
It’s a shame.
He would love to see Senku’s face right now. This is his most ambitious scientific project yet, and somehow he won’t even get to see the reaction of the person it is supposed to be for, live and in person.
A tired yawn makes his eyes water as he carefully tries to stretch, still fighting against the protests of his sore muscles.
Goddammit.
He is experiencing the first modern-day body switch in the Stone World, and he can barely move without grimacing in pain.
Chrome, sniffing out the sweet scent of discovery the way someone might smell petrichor in a storm, suddenly opens his eyes wide.
He sits up like a man possessed, frantically searching the cave for any sign that his mentor in science is still the same person he has always been.
To his delight, it is Gen who looks back at him through Senku’s eyes.
As someone who tends to be cautious above all else, Gen had the foresight to warn Chrome, along with Ruri, about the possibility of an upcoming switch on Senku’s birthday. Chrome had secretly carried that information with him into the cave, patiently waiting for the chance to confirm it.
Obviously, that doesn’t make it any less incredible.
Gen snorts and smiles, playfully elbowing Chrome and urging him to keep it a secret from Magma for as long as the switch lasts.
Chrome, proving that a practical, collaborative lesson is far more effective for children than a simple explanation, grins from ear to ear and spends the rest of the day subtly offering his help with the heavier tasks.
Much to the confusion of the muscle-bound member of their group.
Before they know it, the sun begins to set, and they have to head home.
The rocks on his back are, unsurprisingly, incredibly heavy—much more so for his current body.
Perhaps he wouldn’t be struggling quite so much in his original body. After all, his father, Stanley, trained him from childhood in the art of carrying heavy things.
But since there are still several hours before the switch and he desperately wants to get back, he has no choice but to let out a resigned breath through his nose and keep walking.
He looks inquisitively at Magma, who has explicit orders to get Senku—or rather, Gen in Senku’s body—back to the village before sunset.
But time passes.
The sun sets.
And Magma shows no sign of doing anything about it.
Chrome, considerably less subtle than Gen, kicks Magma in the ankles and very obviously jerks his head in Gen’s direction, as if reminding him that there is something he is supposed to be doing.
Magma, being the idiot that he is, opens his mouth as the sudden realization hits him.
Then he attacks.
He blindfolds Gen and throws him over his shoulder.
The weight in his back, shoulders, and legs is immediately replaced by the beautiful sensation of freedom, making him curse Magma internally for taking so damn long to kidnap him.
He hears Chrome shouting and Magma laughing as they race toward the village, but he can’t bring himself to care very much.
The next time he opens his eyes, he will be looking at himself through someone else’s eyes.
And the cycle will be complete.
For now, he simply lets himself be carried, ignoring the dampness gathering in his palms from nerves.
He is standing on a metaphorical platform, watching a train accelerate recklessly toward him.
But he’ll cross that bridge when he gets there.
Those minutes end up feeling like seconds.
Before he knows it, the murmurs around him grow louder, telling him they have arrived.
He feels Magma climb the precarious wooden staircase leading to the observatory with an ease that doesn’t quite match the difficulty of carrying a person over his shoulder.
Inside, his nose immediately recognizes the familiar scent of flowers from his own clothes.
From his own body.
He is standing face-to-face with himself, blindfolded, his heart pounding against his ribcage.
He’s home.
Senku, very obviously imitating the way he talks, welcomes him in an ominous voice, pretending he is about to hand him over to the Empire of Might.
Gen, who is first and foremost a phenomenal actor, plays along with almost astonishing naturalness, endlessly entertained by whatever his soulmate comes up with.
Someone removes his blindfold.
And instead of seeing his own face, he sees Saturn.
He built that telescope himself, so he knows perfectly well that it is impossible to see Saturn through it when they can barely get a clear view of the Moon.
And yet, there it is.
Right before his eyes.
Just like every other impossibility he has been forced to deal with in his daily life.
Beside him, Senku smiles through his body, with his own lips and his own eyes shining with understanding.
But he says nothing.
Everyone else in Ishigami Village wishes the wrong person a happy birthday and then leaves for the night, planning to continue building the cell phone the following day.
Senku, still pretending to be Gen, slips his hands into his sleeves and stays behind, as though this has always been where he belonged in the world.
And maybe it is.
“You never told me your birthday,” he says.
It still feels strange hearing his own voice.
Well.
Time to confess.
“I didn’t need you to. You gave me the number of days, and that was enough. I calculated the rest myself.”
He doesn’t mention that he had to do it several times because he kept thinking he had gotten it wrong.
Because what were the chances that their birthdays would be palindromes?
His own face looks back at him, confused features and furrowed brows creating an expression far more characteristic of Senku than himself.
“The tree,” he clarifies, as though it should be obvious.
Then he turns his gaze toward the starry sky, searching for enough courage to state the obvious.
“Once I saw your handwriting on that tree, I knew it was you.”
Senku exhales through his lips, making the mark along his cheek shift slightly.
“Isn’t that a little cheesy, Mentalist?”
Gen shrugs, a mocking smile tugging at the corner of his lips.
His entire body still aches like hell, but here, in the observatory he designed and built for one of the most important people in his life, he can barely feel it.
Senku toys with the characteristic white strands falling beside his own face, no longer dyed, as though he has known them his entire life.
Gen figures it might be some kind of nervous impulse, just like his sweaty palms.
But he finds it so endearing that he lets him continue.
These are their final hours in each other’s bodies.
Tomorrow, they will return to their own bodies and never leave them again.
He still remembers almost nothing about his first switch, but since this one will be different, he takes Senku’s hand in his own body and leans forward to press a kiss against his own cheek.
Yes, tomorrow they will be themselves again.
But for now, they are determined to discover as much about each other as they possibly can before the night is over.
Even if that means ignoring how incredibly weird it feels to kiss yourself.
Outside, the stars shine brighter than ever, eager to be observed through the first telescope of the Stone Age.
A telescope that, unfortunately, is being left for another occasion.
“Wait,” Senku says, pulling away from Gen for a moment, his breathing slightly ragged.
“So you’re Dr. Xeno’s son?”