Chapter Text
Ryusui was always the right choice. He’s strategic and brilliant, insightful and ambitious. Gen says his jovial nature keeps everyone’s morale up. He knows his stuff, truly and deeply, in the same way Senku knows chemistry, Gen knows people, and Chrome knows the earth.
Minami warned Senku when they were looking for a captain that he might not be the right fit. She cautioned that his ego, intensity, and unrelenting pace could clash with the fragile equilibrium they needed to maintain, that his greed and his personality could overwhelm them all. But Senku had made his call, and he stands by it. Ryusui gets results. He commands loyalty. He leads.
And he is, also, an absolute menace.
Without Francois to temper his chaos or Gen to run subtle interference, Ryusui veers into feral territory fairly quickly. He’s explosively loud at all hours of the day, constantly pacing the camp, stopping by all workstations, pushing for faster progress, stronger engines, more aggressive logistics, quicker location of the oil. His dream ship is finally becoming real. The world is new and raw and shining, and it’s gone straight to Ryusui’s head.
He needles Senku relentlessly - not just about engineering schematics and propulsion efficiency, but about his emotional state, his silence, his heartbreak, what Gen said. When subtle hints don't work, he escalates into outright pestering. Ryusui treats emotional repression like a technical fault he’s determined to correct with sheer persistence and noise.
He’s making it rather challenging for Senku to nurse his broken heart, mostly because he keeps wishing Gen was here to mitigate the worst of Ryusui’s impulses. It didn’t make sense to send Gen away to the camp on an ostensibly culinary endeavor without Francois, who really is the only competent cook they have. Right now, though, it feels like another one of Senku’s many mistakes.
He’s still not sleeping well. It’s apparent Yuzuriha and Ukyo know something is wrong. She keeps sending him concerned looks, and Ukyo will often send him a glance, head cocked, like his amazing ears are listening to his thoughts, and not just the continued, regular beating of his broken heart.
But there's no time for self-pity. They’re working against the clock. The ship has to be finished, sooner rather than later. The next leg of the mission depends on it. Besides, work is soothing. Senku can’t do the calculations of where he went wrong with Gen. He’s not good enough at reading between the lines to write an essay on what he misread. He can, however, design some stupid cool machines.
To that end, Senku throws himself into the next problem: the oil. Without it, the engine designs are just drawings. Without combustion, propulsion is a fantasy. The deeper they go into industrial replication, the more the need for fuel becomes urgent.
He’s already sent Kohaku to scout the areas near Ishigami Village. She’s due back any day now, and when she returns, Chrome and Ukyo will join her for a more targeted expedition. With any luck, they’ll narrow down the territory and find the Sagara oil fields.
In the meantime, Senku’s caught in a smaller but equally frustrating battle: cabin design. Ryusui has been redrawing layouts daily, obsessed with optimizing for comfort and privacy. Admirable goals - if they didn’t keep cutting into the space allocated for Senku’s lab car. The latest revision has blocked off the backdoor access entirely. The only way in now is through the top hatch.
Senku grits his teeth and redraws the schematic.
Ryusui snaps his fingers inches from Senku’s ear. Senku’s pencil jerks on the page.
“I desire for the whole crew to only have to pair up with one other individual!” Ryusui booms.
Senku doesn’t look up. “It ten billion percent has to be at least four to a cabin, or there’s no room for the lab car.”
“You’re much grumpier without Gen,” Ryusui observes, undeterred. His eyes glint. If Gen were here, he’d have defused this three steps ago. He’d nudge the conversation away from its incoming disaster vector before Ryusui really got going. But then again, if Gen was here, things would be different, and they wouldn’t be having this conversation at all. “Maybe we should bring him back early.”
Ryusui’s face splits into a wide grin, like the Cheshire cat. Senku’s never much liked Alice in Wonderland. “Unless you’ve truly given up on Gen? I value Gen's talents very highly! If you won’t keep attacking until you bring his walls down, I’ll go for it!”
“No!” Senku snaps, looking up at Ryusui. His grip on his pencil is so tight that his fingers ache. “He rejected me. Leave it alone.”
“And yet you still desire him!”
It’s early evening, and most of the Kingdom is distracted preparing dinner. Kaseki is remeasuring something for the ship; Chrome is off doing god knows what. Senku laid out his heart only a day and a half before, only for it to fall out of Gen’s careless fingers and shatter on the floor.
“Of course I still want him,” Senku chokes out. “I want him so bad it hurts. But if he doesn’t want me, there’s nothing I can do.”
It feels like weakness to say this. He hasn’t told anyone at all. It’s been something he’s kept locked inside of him, next to the longing for his dad, the terror he has that they’ll never find the petrification mechanism to bring back Tsukasa, the anxiety that hits him when he looks up and can’t immediately see another person. These awful, dark, squirming feelings that remind Senku how insignificant he is in the face of time and space and loss.
Gen had seen all those sides of him. Gen would ask him what his dad’s favorite constellation was. Gen would reassure him that while nothing is certain, Tsukasa went into cold sleep with faith that Senku would try everything he could to bring him back. Gen would notice when Senku’s shoulders went tight and purposefully breathe a little louder, so Senku could hear him over the irrational rush of fear that flows through him when the world is a little too quiet.
“It’s not like you to give up!” Ryusui muses, striking a thoughtful pose. “And that’s not what I would think Gen would say!”
“Then you were wrong,” Senku mutters. He drops his pencil and flexes his hand. It aches. So does everything else. The cabin design will have to wait.
“Hm, no, that can’t be it,” Ryusui says seriously. “I’m often right.”
“Well you weren’t this time!” Senku snaps. “Stop poking at it, Ryusui! I- I can’t do anything about it! I just have to accept that Gen doesn’t feel the same and learn to live with it!”
Ryusui’s mouth hangs open, eyes wide, and Senku draws back, flushing with embarrassment. “I’m not like you,” he says tightly, voice low now. “I don’t just… want , and then take. My desires can’t bulldoze reality. I just have to replace them with rebuilding the world. A world where everyone can come back. Where Gen can be happy. With someone else.”
“I didn’t -” Ryusui starts, but Senku can’t listen anymore. He turns on his heel with a frustrated sound and storms off into the trees before he does something even dumber.
The moment he’s out of sight, the unease creeps in. It’s always there now, this prickling sense of wrongness when he’s alone too long - a remnant, maybe, of the six months alone in the woods, or the millenia in the stone before that. He swallows against it and keeps marching, feet kicking through damp leaves, like he can outrun the fire burning in his chest.
There’s a soft rustle in the underbrush - a presence so quiet it barely disrupts the sound of wind through leaves. But Senku doesn’t need to look to know who it is. He sighs, not stopping, but not increasing his pace either. Ukyo drops out of a tree and falls into step beside him like it was prearranged.
“What’s up, sonar-man,” Senku says, his voice flat.
“The sky,” Ukyo replies drily, and then ruins it by laughing at his own, awful joke. Senku doesn’t laugh, but his mouth twitches despite himself as Ukyo’s giggles trail off. It feels reassuring, walking through the woods with someone else, despite how much Senku wishes everyone would leave him be.
“Ryusui’s pretty good at poking sore spots,” Ukyo says after a long moment, still keeping pace next to Senku.
“That’s one way to put it,” Senku grumbles. “He can’t take a fucking hint.”
“We’re just worried about you,” Ukyo says. “And I think Ryusui feels responsible for pushing Gen on this - he was the one who started this, by asking when you guys got together.”
Senku stops, and closes his eyes, breathing through the spark of pain that unleashes inside of him. When he opens his eyes, Ukyo has paused next to him, patiently waiting.
“You don’t have to say anything,” he offers gently. “But you don’t have to carry it alone, either.”
Senku exhales slowly. “He was surprised, and said I couldn’t mean it,” he says at last, his voice flat. “It’s not a no. But it’s not a yes.”
Ukyo nods, like he understands exactly what that feels like.
Senku stares down at the dirt. “I calculated every possibility a long time ago. I thought I could be prepared for any outcome. But I didn’t account for how much I’d want him to say yes.”
Ukyo doesn’t answer right away. He stands beside Senku in the hush of the trees, hands tucked into his pockets, head tilted slightly toward the sky as if listening to the wind.
“I get it,” he says softly. “It’s not the rejection that hurts the most. It’s the hope. One of the guys in the SDF used to say this phrase all the time - it’s the hope that kills you. Usually after he lost his paycheck at pachinko.”
Senku’s jaw tightens, but he doesn’t respond.
“I always hated that line,” Ukyo adds. “It’s defeatist. If you don’t hope, you never get that moment where everything works out. That rush, that joy, when the world bends just right around your desire.”
He offers Senku a wry little smile. “I think it’s even more important, these days. We need to continue to have things that we want to hang onto. It gets us through the dark.”
Senku makes a humming noise. Slowly, he starts to walk again, in the direction of the main camp. He takes the long way. Ukyo follows, keeping just within the edge of Senku’s line of sight as they walk through the darkening forest.
After a while, Ukyo adds, “For what it’s worth, I think Gen’s just scared.”
Senku raises an eyebrow. “Of what?”
“Of being seen and loved, I think. He's not used to being honest and having that honesty met in kind. You’re the one person who never lets him spin bullshit around you. That’s probably more terrifying than rejection.”
Senku’s mouth twitches again. “Yeah, well. If he’s scared, he could’ve said that instead of treating my feelings like a glitch.”
Ukyo gives a small, rueful shrug. “He’s human. Even Gen panics sometimes. None of us are who we used to be. This world pulls parts of us to the surface we never thought we’d have to meet.”
Senku exhales again, slower this time. “Ten billion percent hate that that makes sense.”
“Yeah,” Ukyo says. “Me too.”
—
Kohaku’s back by midday the next morning. Senku spots her when he ducks out of the workshop to grab some water, his hands still stained with graphite and oil from the latest round of design compromises. She’s standing at the edge of the campfire circle, speaking with Yuzuriha and Ukyo. Her arms are crossed, her weight on one leg, and she looks like she’s just finished making a very firm point.
He’d like to think they’re talking about something work-related - again, they really need to find the oil - but the presence of Yuzuriha alongside Ukyo and Kohaku means it’s definitely about Gen.
Ukyo tends to keep his mouth shut - he’s not one to gossip. But Kohaku absolutely is, if she thinks it’s to someone else’s benefit. If she thinks sharing sensitive information will help someone she cares about, she won’t hesitate, even if it means blowing past Senku’s tightly guarded privacy like it’s made of rice paper.
Senku had intended to get a snack alongside his water - he’s still struggling to eat, and he’s already dropped about a kilo since that night by the fire - but he finds thinking on what they’re saying is tightening his stomach and he ends up walking away empty-handed.
He’s checking on the balloon’s basket when Kohaku corners him. He jokes about her being a lioness, but he genuinely does feel like prey as she stalks across the clearing, eyes narrowed, gaze fixated on him. She’s holding a plate of food - deer curry, it looks like, with potatoes, onion, and carrots. Senku raises an eyebrow as she heads in his direction, stepping away from the balloon just in case.
“Lioness,” he says, and she scowls at the nickname but doesn’t slow down. “What’re you-”
Senku stumbles back with a startled yelp as Kohaku tackles him to the ground. He lands against the side of the balloon’s basket with a dull thump, but she’s somehow managed to keep his head from hitting anything harder than her forearm. Her knees press into his chest, pinning him - not painfully, but immovably. The plate of curry in her hand doesn’t so much as wobble.
“What the fuck are you doing?” Senku asks. Kohaku smirks at him and picks up the spoon from the plate.
“Feeding you, since you’re too much of a dumbass to manage it yourself,” she says, scooping up some curry.
Senku opens his mouth to respond, and Kohaku takes advantage of this to shove the food into his mouth. The curry’s not amazing - when Francois isn’t around, it falls mostly to a bunch of modern-timers who relied had heavily on takeout and instant food for sustenance in the old days, and seem mildly perplexed by the process now. The curry’s too heavily seasoned, the deer somewhat disgustingly gamey. Yet the moment the food is in his mouth, Senku’s forced to admit Kohaku made the right choice. Hunger had been lying dormant within him, but even this overcooked curry tastes incredible.
“You’re losing weight,” she says bluntly, already scooping up another bite. “Yuzuriha’s worried. Ukyo’s worried. I’m pissed.” Senku tries to sit up, but she presses him back down easily. He’s no match for her physically, and she knows it.
“I didn’t ask you to - ”
“You didn’t have to,” she snaps. “That’s the point. You’re not a machine, Senku. You don’t get to ignore your body just because your heart’s been wrecked.”
Senku narrows his eyes at her. Kohaku watches him with something like sympathy, but she doesn’t offer platitudes - she’s not really the type, especially when there’s a more direct route she can take. She just lifts another spoonful threateningly.
“Eat,” she says. “Then we can talk about him. Or not. Your choice.”
Senku swats her hand away. “Get off of me and I’ll eat,” he grumbles. Kohaku raises a brow but shifts off him, still holding the plate like she doesn’t quite trust him to follow through. He sits up slowly, adjusts his legs, and snatches the plate from her with a muttered curse. He takes another bite - larger this time - and exaggerates the chew with deliberate slowness.
“Happy?” he grumbles. Kohaku ignores him. He’s reminded, strangely, of the time he got sick with the flu when he was eight and Byakuya stayed home for a week straight, feeding him ramen and watching anime with him. His dad had been horribly sick the week after - sick enough that Yuzuriha’s parents had had to take Senku to their house for three days to give Byakuya the space to recover.
“I had a little chat with Gen yesterday,” she says.
“Did you threaten him like Yuzuriha did?” Senku asks, taking another bite of curry.
“There wasn’t really a need to. He’s been beating himself up pretty hard.” Senku’s traitorous heart squeezes at that. “So we had a nice little talk. I think I’ve managed to talk some sense into that rat bastard.”
“You didn’t need to do that,” Senku grumbles, cutting a potato in half a little more viciously than he meant to. “It’s fine that he doesn’t feel the same way.”
“Don’t be a wombat,” Kohaku says. Sometimes, the villagers have just such a weird use of language that Senku wishes he’d already revived a linguist to understand how much has shifted from their time to now. Japan has no native wombats. He wonders what Kohaku thinks they are. “He does feel the same way, actually. He’s just an idiot who didn’t think he was capable of love.”
Senku takes another bite of his curry. “Seems like you’re just trying to make me feel better,” he says irritably. “I’m fine, lioness. Feelings were just going to distract me, anyway, given the stupid amount of work we have to do.”
He’s reminded, for a moment, of the pulley system, the one he’d rigged to save her from under that tree when they first met. Back then, she’d looked at him like he was a miracle. Now, she mostly looks like she wants to drop-kick him into the nearest river.
“This seems to be something dumb related to being from your old world,” Kohaku says. “Let me tell you something, science boy. My world is one where people can die easily. We’ve had famines that have wiped out a good chunk of the people I knew. I’ve spent a lot of my life getting estranged and working myself to the bone to keep Ruri here. Life is too brutal to not revel in the joy when you can find it.”
She pokes Senku in the chest, so firmly it almost knocks him back a little. “And you, you little slimeball, need to stop acting like you’re totally fine and okay with all this. It’s okay to be mad at him, and it’s okay to want things for yourself.”
Senku just stares at her and takes another bite of his food.
“Or do whatever you want,” Kohaku says eventually. “Just don’t to the point where you’re as irritating to deal with about this as Chrome is with Ruri.” She stands up and dusts off her knees. “I’ll come get the plate later. If you haven’t eaten all of it, I’ll force it down your throat. Now if you’ll excuse me, I have oil to go find.” She smiles cheerily at him and dashes off.
Senku watches her disappear into the forest, the underbrush parting around her like it’s learned not to get in her way. The sounds of camp slowly creep back in - someone hammering wood, Kaseki’s noises of delight, Ryusui’s boisterous laugh. It’s enough signs of people for Senku to not feel totally isolated.
He glances down at the curry in his lap. The food’s going lukewarm, but it still smells decent enough - in as much as it can. He shovels in a few more bites, chewing without caring much about the taste. His focus is still tangled in the conversation that just happened, in the sharp, raw edges of what Kohaku had said.
He does feel the same way, actually. He’s just an idiot who didn’t think he was capable of love. Her summary of her conversation with Gen was so direct, and felt so designed to appeal to what Senku wanted to hear.
He scowls, then stabs the last chunk of potato like it personally insulted him and eats it out of spite.
The problem is increasingly becoming not that Gen doesn’t feel the same. The problem was that he might, and still broke Senku’s heart anyway.
He sets the empty plate aside, leans back against the balloon basket, and stares up at the sky. The sun’s at its midpoint, another day halfway gone. Another dozen problems remain unsolved. They still don’t have any ideas of where the Sagara oil fields are, even though it’s a good thing they ruled out some obvious areas around Ishigami village. Ryusui’s probably taken advantage of his disappearance to edit the cabin layout again. His heart is apparently a live wire with no off switch, crackling out of control every time he even thinks about Gen.
He lets out a groan and slaps a hand over his eyes.
“What a pain in the ass,” he mutters to the sky, to no one, to the tangled mess of to-do lists and emotion buzzing under his skin.
The sky doesn’t answer. It just keeps stretching out above him, endless and unbothered.
—
He misses Gen coming back to the camp, mostly because Ryusui always commands all the attention in the room, and Gen is very good at avoiding being noticed if it suits his purposes. Senku had let other people take the lead on scheduling with Francois and Gen, and hadn’t asked for details.
He’s currently trying to keep Ryusui away from the blueprint again - they've resolved the argument about cabin sizes, but now the fight has turned to the sizing and placement of the engines. Kaseki and Chrome, who really should also have opinions on this, have mysteriously disappeared, so it falls on Senku to fight with Ryusui.
Senku opens his mouth, ready to eviscerate Ryusui with hard numbers and structural integrity - and is abruptly yanked backward by the collar.
Taiju, looming and unyielding, has one massive hand on each of their collars like they’re a pair of scrapping alley cats. “No fighting!" he bellows, loud enough that Ukyo, wherever he is, is probably wincing.
Senku sighs, only marginally resisting the urge to go limp like a disgruntled kitten. He hates when Taiju does this, largely because it reminds him how weak he is compared to that ridiculous mountain of a man.
Ryusui, predictably, laughs it off like it’s all a game. “You’re right, Taiju! We should channel this passion into teamwork!”
Senku groans. He’s too tired for this level of diplomacy. He twists slightly in Taiju’s grip, trying to regain some semblance of dignity as he straightens his coat.
He notices Francois, standing off to the side, looking as calm as ever despite clearly having been the one to sic Taiju on them, and can’t stop himself from tensing up. Gen’s not in his line of sight, but there’s no way he’s not here, somewhere. He doesn’t see him, though, and Senku is determinedly acting like nothing is wrong, despite the fact that most people are clearly aware something is.
With Taiju overseeing them like a disappointed kindergarten teacher, Senku and Ryusui manage to hash out the engine design with variations depending on the quality and amount of oil they manage to get from the Sagara oil fields, assuming they can ever find them.
The day bleeds away like an untreated wound, and Senku gets so involved in designs and plans that somehow he does forget about Gen. Work can be like this for him - so all encompassing that he can separate himself from his humanity. Since that night by the fire, when Gen broke his heart, it’s been harder to find that flow state. He’s so buried in it that he can’t even think to feel relieved.
It all comes rushing back in the evening, when he finally manages to recall that he has to eat and should go over to where dinner’s being cooked. The successes of the day blanket him, and he feels better than he has in days, even though he’s still deeply frustrated by the lack of progress on finding the Sagara oil fields. Kohaku, Chrome and Ukyo have plans to go exploring tomorrow, and they’ll need the balloon for that, possibly the cameras too.
When he enters the camp, he’s still trying to map out everything they’ll need and what he has to do to get it all ready for them. And then he sees Gen. He’s cutting bread with calm precision, his expression unusually focused, brows slightly drawn. He looks thoughtful and calm. The firelight catches on the edge of his cheekbone, the curve of his throat. He looks up at that exact moment, eyes locking with Senku’s across the campsite.
And all the warm, terrible, wonderful things Senku’s tried to lock away come flooding back in.
The soft evening light turns gold as it washes over Gen’s skin. He’s bathed in it - sharpened and haloed by sunset and firelight, like some mirage carved out of memory and longing.
Senku almost stops walking, heart thudding against his ribs, his carefully constructed plans crumbling into ash at his feet. It takes him a second to get control over himself, and he forces himself to sit down next to Kaseki and start talking about how the new forge is treating him.
He keeps Gen in the corner of his eye throughout dinner. Irritatingly, his appetite is gone again, but Kohaku is glaring at him and he really doesn’t want to be sat on again, so he forces himself to eat all his fish and the slice of bread he was given.
He intends to eat and disappear back into his work, but Ukyo and Kohaku corner him with questions about the balloon for their oil-finding expedition, and he gets lost in the plans. He’s so distracted that he doesn’t notice Gen until he’s right next to him.
“Dear Senku,” Gen says, and even Senku can pick up the quaver in his voice. “May I speak to you for a moment?”
Senku has trusted Gen since the moment he met him. He’s followed Gen’s lead time and time again. Despite his heartbreak, he looks at him - his bicolored hair, his sharp gray eyes, the firm set to his mouth that can’t hide how nervous he looks - and knows, deep in his soul, there’s not much he can deny him.
Somewhat despite himself, he nods, and follows Gen wordlessly, like gravity has shifted direction and Gen is the only fixed point left.
—
The world feels like it’s fundamentally realigned now. It’s like Senku’s discovered a new theorem of reality - he’s solved all the mysteries of time and space, united quantum mechanics and relativity, knows how the universe began and how it will end. He’s not the same person he was this morning.
For the first time in two weeks, he shares a tent with Gen. For the first time ever, they also share a futon - huddled together beneath the covers as lightly as they can get, despite the heat still lingering in the evening air. In the dark, he can just make out the gleam of Gen’s eyes, soft and steady, watching him like he’s the answer to a question too old to name.
Senku’s never really been one for words. Equations, yes. Chemical symbols, blueprints, force diagrams - those he can recite in his sleep. But language has never been his strong suit. He’s blunt and to-the-point, a little crass, direct to a fault. Metaphors and similes are lost on him.
Here in the dark, he wishes that wasn’t the case. Down on the beach, by the tantalizing beginnings of their ship, Gen had breathed hope back into Senku’s heart, sealed it in with his lips. Senku had been stunned into silence, the flood of feelings between them only being able to be summed up as “cringe”.
Ah well. Gen knew what he was getting into.
“You need to sleep, Senku dear,” Gen whispers, trailing his fingers along Senku’s arm and leaving goosebumps in their wake. He’s never really liked people touching him much, but it’s never been an issue with Gen.
The night can still be overwhelming. In the dark, when he wakes, it’s reminiscent of the millenia in the stone - unable to move, all alone, stripped of his future and robbed of his past. But now, when the dark closes in, he reaches out - and Gen is there.
They had said they’d go to hell together. Senku drifts off to sleep, knowing now they’ll go there hand-in-hand.