Work Text:
It does not, surprisingly, happen by accident.
Everything in Senku tells him this is illogical , that this isn't the right time, that humanity comes first-
That his Dream comes first.
But there's something almost more promising in the legacy of blood and love Gen is asking of him than of anything he will do in his acts to martyr himself to humanity.
Foolish. So fucking foolish, what men will do for love. For a legacy.
Senku doesn’t even know what he wants, anymore.
"Do you ever think about having kids?"
Senku chokes on his spit, fumbling with the beaker in his hands before setting it down heavily.
It cracks, splintering across the sides and spilling hydrochloric acid all over his workspace.
"Shit!" He curses and grabs a stray rag, trying his best to wipe everything down in spite of the tremble in his hands.
Gen watches on, an amused smile curling at his lips.
He remains mercifully silent, allowing Senku enough time to digest the charged question.
Senku, to his credit, handles it with at least a millimeter of grace.
"I guess, don't most people? Why?" He turns away from Gen's piercing gaze, knowing he's avoiding the question.
Senku isn't most people , especially not with his current responsibilities as chief and champion of humanity, but he won't lie and say that he doesn't want to be.
He can be selfish.
(Gen makes him feel selfish.)
Next to him, Gen sighs, a fond huff and a hint of wrinkles around his eyes.
"I'd like to have some, someday.” The unspoken with you sits between them, gently imploring but not judging. He’s not talking about adoption, although Senku reasons he’s not not talking about it, either.
Senku stills in his half-turned position and risks a glance to the side. Gen's smile is still a bit too Cheshire, too much like he's giving a show, but there's a vulnerable edge to it.
Like he already knows the answer.
Senku swallows, the back of his throat drying up. This is a dangerous conversation.
He's not sure what the right answer to this is, but he certainly knows what the wrong one looks like. The kind that would make Gen wary and distant, that would fester like a wound and never really heal.
And Senku is nothing if he’s not stubborn, if he’s not pushing away every distraction, anything that can get in-between him and space. Gen was an exception, he would admit, but just barely.
But.
He drops his gaze back to the mess and tightens his grip on a shard of glass, enough that it threatens to break the skin. The sting is sharp but fades in a flood of endorphins and the loud beating in his ears.
As if Senku has ever been able to deny his mentalist.
"I'd like that,” he whispers. “With you. Kids.” He's surprised at how easily it comes, how it barely even sounds like a lie to his own ears.
He's hardly a wordsmith, and he's afraid any attempt at subtlety wouldn't convey what he actually wants to say. He tries, and he hopes that it is enough.
Gen flushes, and his smile shakes and wobbles, unsteady. His eyes soften, just like they did the first time Senku choked out an I love you without finesse or planning, an incoherent mess of words and emotions that made no real sense.
Gen loves that kind of stuff, the sappy shit you’d find in a movie marked down by 80% in a bargain bin of a chain store.
Something close to relief unfurls in Senku's chest, his brain overloaded on serotonin and the same crap Taiju must’ve felt for years.
It must have been the right answer.
The pain in his hand only comes back into sharp clarity after Gen leaves.
One late evening, Gen slips under the blankets next to him.
"It's been two weeks."
They've had sex before.
Many times, in fact. In many places, not limited to Senku's hut, the observatory, the lab (to Chrome's loud and dramatic disapproval), and a few particularly heated encounters outside.
" Senku, please," Gen moans, breaking their kiss to claw at his clothing.
But it's different when they're trying to make a child together.
Senku snorts, nerves settling as he tugs his clothing over his head, Gen's robe soon following.
"Why d'you have so many layers on anyway?" Senku grouses, fiddling with the makeshift obi for a second too long. It's a familiar song and dance, one that keeps him grounded.
His hands shake.
He's really doing this. With Gen.
"It certainly came in handy with Magma, don't you think?"
Senku winces.
"Besides, I sunburn easily," Gen laughs, shrugging off the tense mood just as easily as he had created it.
Senku doesn't respond, focusing his attention on getting Gen undressed.
His hands impatiently tug the rope away, revealing Gen’s pale skin.
Underneath the moon, brighter than it ever was in Edison's world of light almost 4,000 years ago, he looks almost unearthly.
His eyes linger over at the raised pink scar on Gen's abdomen. After a moment's consideration, he leans down and presses a soft kiss to it. He hovers for a moment, studying the soft curve of the ribs right beneath Gen’s skin. It’s an apology and a thank you and an I won’t let this happen again, but he’s sure that it doesn’t come across that way.
Gen snickers, pressing a single finger to his forehead, gently pushing him back.
“Didn’t take you for such a sap.”
Senku frowns, gently thumbing at the edge of the wound, wondering about what-ifs and all of the unhappy endings they could have had.
We got really lucky is what he would say if he believed in luck.
“Hey,” Gen says, voice soft, “Don’t be like that."
Senku pulls away.
Gen shucks off his pants unceremoniously, kicking them away from himself. He pauses, underwear caught around his ankle. “I’m going to need new clothes soon,” he jokes, toeing it the rest of the way off.
His legs splay in an invitation, and Senku doesn’t hesitate to fit himself in the warm space between Gen’s thighs.
Senku cracks a small smile. "Looking forward to being fat?"
Gen gasps in mock offense, pushing Senku back with a firm foot to his chest.
"A baby bump isn't fat, Senku-chan!"
"Yeah yeah, I know, drama queen." Senku’s voice sobers at the reminder. Parenthood is yet another unknown, another thing he’ll be able to share with Gen.
Another attachment that will keep him on the ground.
Gen catches this, leaning up to hook his arm behind Senku's neck so he can drag him into an unhurried kiss.
Senku runs his tongue across the seam of Gen’s lips, groaning happily when they part for him. His hands wander, squeezing Gen’s waist before traveling up and running over Gen’s nipples.
Gen whines into the kiss, squirming away from the touch.
“Sensitive,” Senku says as he pulls away, tweaking one until it's red and puffy. He amuses himself by squeezing and playing with his partner’s chest for a moment.
“They’re so soft-”
Gen slaps the offending hand away, pouting when Senku chuckles. His annoyance is apparently short-lived, as he grabs the other one and drags it lower.
“Oh? Someone’s impatient.”
“Shut up,” Gen groans, pulling Senku into another unhurried kiss.
Senku obliges, his hand busying itself with the space between Gen’s thighs, brushing his fingers against the soft folds of his sex.
Against him, Gen makes a pleased noise, melting into the touch. His entire body shivers when Senku’s calloused finger presses insistently against his clit, the others hooking back to rub against his hole.
“C’mon Senku-chan, we can just skip the foreplay, ok~?” Gen pleads, rocking down onto Senku’s fingers. “Don’t make me wait.”
Normally Senku would tease, would draw things out just to watch Gen beg and whine and cry, but he’s uncharacteristically swayed.
Maybe he’s a little overeager as well.
He nods, gently easing in a single finger, pumping it in and out before adding another. Gen is practically soaking, eager to fulfill that biological imperative built into almost all life on Earth.
“Please please please please~” Gen chants, head rolled back and arms forcing Senku to remain as close as possible.
“Alright, I’m gonna give it to you, ok? Calm down,” Senku says, fucking his fingers up into Gen’s soft cunt a few more times before he relents, withdrawing them.
Gen trills, hooking his legs around Senku’s waist.
Senku pumps his cock a few times, hissing at the attention after neglecting himself for so long. “Ready?”
“Mmmhm.” Gen leans up for a soft kiss, a gentle hand caressing Senku’s face. “Want it.”
Senku swallows, feeling his face heat up at the response. He presses forward, sliding in after only a little pressure. Gen is wet and ready for him, the soft flesh giving easily underneath Senku’s ministrations.
His breath hitches, and he bows his head to leave a chaste kiss against Gen's neck, staying there until he's sunk all the way in, their hips pressed flush together.
Senku savors the moment, rolling his hips only slightly. He's rewarded with a soft moan and fingers tangling in his hair, pulling him closer. Gen’s legs draw tight around his waist, keeping him locked inside.
“Can’t move if you do that,” Senku sighs, rocking his hips as much as he’s allowed.
“Mmmm,” Gen replies intelligently, but he loosens his hold a bit.
Senku settles his weight on his forearms, bracing himself before drawing out as far as possible, pushing back in with one long, uninterrupted stroke. He can already feel sweat running down his chest and shoulders, evidence of his own lacking stamina.
Gen isn’t faring much better, the anticipation of the evening evidenced by his walls clenching and shuddering around Senku’s cock.
“Won’t--- won’t last long if you do that,” he grunts, picking up the pace, already feeling the telltale signs of his release curling in his lower body. “Gotta relax for me if you--” His voice cuts off with a moan as Gen squeezes around him purposefully.
“Want it as soon as you can give it to me,” he says, meeting Senku’s stuttering thrusts.
Senku leans down to press a firm kiss against Gen’s soft lips, their movements rapidly becoming messy and uncoordinated. When they break apart, Gen’s eyes are glassy, tears threatening to bubble over onto his cheeks.
“Guh-Gimme a baby--” Gen shudders, clenching hot and tight around him before he’s sobbing through an orgasm. Hands cling to Senku’s shoulders, eager to minimize the space between them.
Senku follows, the reminder that they’re creating a life together all too much to handle. He thrusts once, twice, before his hips press as close as possible against Gen as his orgasm rolls through him. He feels hot and dizzy, losing himself in the sensations as his vision gets spotty.
When he comes back to himself, the night feels dangerously quiet, save for the heavy gulps of air they're both taking in. Distantly, he thinks he can hear crickets chirping.
Senku stays inside until he's gone completely soft, savoring the simple intimacy of being joined with Gen. When he pulls out, his eyes take in Gen’s fucked out hole, the slow drip of his come leaking out, evidence to what they had just done.
He swallows thickly.
Logically, he always knew there was some merit to love since all of humanity seemed to be drawn to it, but he hadn't known that neurotransmitters and hormones could ever make someone feel like this. Like the rest of the world and the secrets of the cosmos almost don't matter.
Almost.
A soft chuckle pulls him from his musings.
"What's going on in that head of yours, Senku-chan?"
Gen is grinning, as he usually is. It’s a tired, happy thing that makes Senku almost dizzy with joy, his nerves alight with pure flame. Offhandedly, he hopes their child will have Gen’s pretty smile so that even when they’re both gone it will somehow live on.
He swallows thickly. "Do you think we got it?"
His legacy. Theirs, now.
Gen leans up and presses a smiling kiss to his lips. "We should try again just in case."
His voice is teasing, giving Senku room to ignore him and just get some sleep, but he finds himself agreeing despite the ache in his limbs.
"Yeah. Just in case."
One morning weeks later, Gen slips back into bed next to him.
"It's late."
For all his complaining and whining, Gen takes to pregnancy with an odd sort of grace.
When he's not pestering Chrome in the lab or complaining about his sore feet, Gen's usually weaving baskets or sitting with the children, performing simple tricks as entertainment. They all look to him as if he's some sort of minor god and delight when he teaches them a few to show off to the adults.
Involuntarily, Senku's brain presents to him a similar scene, except the children hovering around Gen and tugging at his sleeves have his eyes and Gen’s nose.
It shouldn’t be so frightening.
The village children like him enough, but he knows he’s callous and honest to a fault, something that never endeared himself to children when he was younger. It’s illogical to worry about his child not liking him, but a small voice in his head reminds him of his duties.
His dedication to reviving humanity, his responsibilities as chief.
His dream.
Would they understand? Would his child forgive him if he wasn’t always around, if his attention was split between them and the promise of space?
Would he be able to forgive himself?
Senku tries to be there for Gen, at least as much as a man trying to rebuild humanity can spread himself thin, but he’s no Byakuya.
The late nights when Senku stumbles inside their hut, ashamed, like he's spent the night drinking instead of trying to rework the cellphone are his least favorites.
By then Gen is usually asleep, the soft rise and fall of his chest the only thing letting Senku know he's alive.
He usually gets a lecture over it in the morning from Kohaku and the others, but Gen never begrudges him this.
The guilt is there, though, knowing that he could be doing more for Gen, for their unborn child, yet he continues.
It feels like an omen, like the beginning of a cycle that will repeat until Gen tires of it and he’s left unloved and alone.
They've only talked about it once. Senku wonders if Gen still remembers.
"I knew what I was getting into, the moment I decided to fall in love with you."
It’s almost two years prior, the thrill of new beginnings and the unknown loosening their tongues.
Senku smiles, amused. His hands continue to idly fiddle with his newest project. "Oh, it was a decision? Should I be honored or offended?"
Gen nods, ignoring the latter question. "There's always a point before no turning back, you see. I knew…" he pauses, considering his words, "that I wouldn't be able to have all of you. I decided I was ok with that."
There's a healthy pause in their conversation.
"...I'm sorry," Senku says, unable to offer anything else. He's never been sorry for who he was before, not when he was blowing things up and giving his dad grief, but now he half wishes he could change.
Gen smiles, wide and steady without a hint of jealousy or regret.
"Don't be like that, Senku-chan. I wouldn't be half as in love with you as I am now if you were any different."
Gen is a silver tongue, a filthy liar if Senku's ever seen one. Senku knows how to speak his language, how to give as much as he gets.
He's not sure how to handle him when he's telling the truth.
Senku can make medicine and generators and all manner of things that will propel humanity forward through their history, but he knows the life nestled in Gen's womb trumps all of that.
It's so beautiful , he thinks. Gen is so beautiful.
They're just biological machines, he knows, but there's something beyond the fact that there will be consciousness in this creation, something more than what any AI could ever hope to fulfill.
Sometimes, when Gen is asleep, Senku finds himself indulging in sentimentality.
"I can't wait to meet you," he whispers against the stretched out skin, where a small being that's half him and half Gen lies curled up, safe.
He thinks of Byakuya, of lecturing him and going out to eat ramen together, of asking questions and getting only half-answers.
Senku always misses Byakuya, but now, more than ever, he wishes he asked him how it felt to be a father. What it’s like. If he thinks Senku will ever be able to live up to his ideal.
When he was a child, he was so caught up in his dream that he forgot his father wasn’t forever.
He wants, and he wants, and he wants.
"I promise I'll...I'll take good care of you." He waits for a beat, then adds “Ten billion percent,” for good measure.
Senku does not like to make promises he cannot keep.
He shouldn't entertain what-ifs, but.
But.
Given the choice between the vast unknown of space and the promise of new discoveries, or the warmth of this small room, of the small processes that keep them going for 80 or so years before they stop working...
Senku has never chosen the Easy way out, not even once, but loving Gen may be a first. It's so easy to love Gen. To want to stay by his side. To let himself have this.
Senku doesn't know why he can't convince himself he can have both. He can, he knows it's possible. It has to be.
If not, then…
"...Senku?" Gen must've woken up from his murmuring. He pushes himself up, a feat for someone already as far along as he is, peering curiously at Senku in the darkness.
"I'm here. Sorry for waking you. Couldn't sleep."
Gen huffs out an amused laugh, placing a hand on his belly over where Senku's already is. He's mellowed out during the pregnancy, exhaustion clearly weighing on him. Senku looks forward to Gen being back to his usual self, of being able to pester him in the lab and joke around.
He misses having his mentalist by his side.
"Our little one seems to agree with that."
Senku grins when he feels a tiny kick underneath his palm in answer.
There are times when Senku wishes acutely for the world he once lived in, for its simple and easy joys, for the internet and books and information.
With Gen clutching his hand in a white-knuckled grip, sobbing through another contraction, that sentiment is magnified by ten billion percent.
Senku knows that his knowledge of the human body makes it only logical that he's more directly involved with bringing their child into the world, but seeing Gen in so much pain has made him weak and shaky in the limbs. Kohaku must've seen it in his eyes because she was ready to drag him out to make room for the midwife.
Gen was the one to ask him to stay.
So here he is, sitting uselessly at Gen's side as the midwife tells him to push, to hold, you're almost there.
Senku closes his eyes, overwhelmed. The noises around him become muffled, blended together.
He hates feeling so useless, at the mercy of nature. Modern medicine wasn't even enough to completely conquer one of the most crucial processes for the propagation of their species.
Stupid. Humans could go to space but they couldn’t crack this, not completely.
An unfamiliar shriek pierces the white noise.
Somewhere between the lines of thought running through his brain, he commits it to memory.
He doesn’t want to forget this.
He jolts up, hands closing on empty space, and there's already something blurring the edges of his vision but he wipes it away.
He doesn't want to miss this.
The midwife cradles a squalling newborn and she’s so tiny, already pinkening up from her wails.
He didn't think that something so small, so innocent, could cause so much pain.
Gen struggles into a sitting position and reaches out for her, shaking off the previous hours of labor like he hadn't just been screaming bloody murder the entire time.
The midwife tuts at them, Gen with his wanting hands and Senku’s palpable desperation, taking the time to check their child over and clean her off.
“You’ve waited nine months; you’ll survive a few moments more.”
She turns, wrapping the wailing baby in a soft blanket made by Yuzuriha for that purpose.
Senku’s hands tremble. He’s always been so proud to display every single one of his creations, hold them aloft for everyone to see, but there’s a part of him that wants to take her and hide her away from the rest of the world.
He watches with bated breath as the midwife hobbles over, gently handing the bundle to Gen. She quickly changes out the sheets underneath, replacing them with fresh ones before leaving the room.
Senku swallows, a lump caught in his throat as the baby- his baby - squirms and cries softly as Gen coaxes her into latching.
Senku’s laugh is wet and choked when he sees her face scrunch with effort, mimicking Gen’s signature pout.
They watch her in silence.
“I hope she has your eyes,” Gen admits quietly.
“Oh? I think yours are pretty damn charming, mentalist,” Senku says, brushing his fingers against the soft downy hair on her head. She makes a soft noise, but isn't disturbed from her nursing.
Gen glances at Senku, a lone brow raised. “Well she’s already got my nose and hair, I would like her to at least have something from you.”
“Aw, I think it would be nice having a mini Gen running around,” he teases, lowering his voice when she begins to shift, pulling away in favor of settling into a nap. “She’s so beautiful.”
Gen smiles when she nods off and her movements still.
“She’s going to be hungry again soon.”
Senku makes a noise in agreement, eyes taking in the gentle scene before him.
He knows he’d do anything for her. For them.
When Senku woke up in the stone world he didn’t have much to lose. His era was gone, thousands of years of human history erased, save for what the petrified kept in their hearts and memories. Then came Kohaku and Chrome and Gen and he suddenly had more things to lose, more weaknesses in an unforgiving world.
Fear. That’s what this is, more than when he was in the wild all alone, more than when he faced death head-on countless times.
It feels like he’s letting go of something he’s held onto for so long.
"Would you like to hold her?" Gen's voice is gentle, teasing. He's most certainly caught the deer-in-the-headlights look Senku's sporting, politely choosing not to comment on it.
At least, for now.
Senku sucks in a short breath, eyes flitting over her rounded cheeks and pink skin, the soft black hair covering the top of her head. He doesn't want to blink. He wants this moment to stretch on towards infinity.
"Yes," he breathes, reaching out to gently take her in his arms in an attempt to leave her rest undisturbed. Logically, he knows she isn't made of mica or talc, but he's almost (illogically) afraid she'll slip from his grasp nonetheless.
She makes a small noise and he holds his breath, afraid that he will be of the first in this world to frighten her, but she settles in his hold, breath soft and even.
Senku doesn’t ever want to be apart from her.
"Hoshiko."
Gen smiles, exhausted but plainly happy. “Our little star. How fitting.” His eyes gain an amused glint. “I thought you liked Europa? Or even Byakuya?”
Senku shrugs, turning his attention back to his daughter. “It’s a good name. I’m sure when we have another-” he freezes, voice catching in his throat.
God. Another. He's already thinking about- doesn't even know if Gen actually wants---
He hears a soft chuckle from beside him, which threatens to turn into a full-blown laugh if it weren't for Hoshiko's squirming at being woken up. She whines, and Senku tries to soothe her, but her displeasure from being away from Gen is evident, the noises escalating in pitch and volume.
Gen takes her back in his arms, pushing aside the loose robe he's wearing, hoping to pacify her.
"So eager. And who says I want another?"
Senku looks away, half wishing a hole would open up underneath him. He's so selfish. Gen just went through all of this and he still-- he's not even sure himself--
"I do, by the way." Senku is dragged away from his idiotic self-loathing to Gen, smiling down at the child curled up against his bare chest, warm and content.
"I'll give you as many as you want, Senku, just as long as you save some of yourself for us." His voice is soft and genuine, for once, and Senku doesn't know how he got so lucky.
Senku was never afraid to martyr himself for humanity's cause, and he's thankful that Gen is so understanding, that even still he wanted a child with him.
It feels like breathing for the first time in almost 4,000 years.
“Everything that I am, Senku… it’s always been for you. For this.”
A part of Senku wants to tell Gen that he's made his decision, that if Gen really made him choose between the world and the family he's carved out for himself he'd ultimately (foolishly) turn his back on humanity.
That they're enough for him.
He thinks Gen knows and is just kind enough to share Senku anyway.
Dangerous, so dangerous. He doesn't know how humans survived for so long with the burden of love weighing on their chests, making them weak and irrational.
He looks at Gen, at the perfect being they've made together cradled in his arms.
He thinks of Taiju and the stupid, pure, puppy-dog affection he harbored in his chest all those years.
He remembers his father and the small world outside this room that only exists because Byakuya’s blind faith and love weathered countless generations until it found him again.
Beside him, Gen begins to hum gently, rocking their daughter. She stirs a little before calming, small hands curled up next to her face.
Senku finds himself smiling, something soft and fragile uncurling inside of him and making a home out of his ribcage.
A small part of him wishes that he could go back and let himself know that the stars are beautiful, yes, but life on the ground will be, too. That he’ll one day be ok with leaving the unattainable stars where they are in the cold nothingness of space.
That Senku has a family that loves him and a place he calls home, full of people who will miss him even when he's long gone.
Everything that he is, all for them. For her.
That’s a legacy worth having, he thinks.