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The party is loud enough to carry across half the town. Ryusui doesn't do anything by half, and Francois has somehow managed to source a suitable substitute for champagne.
Luna slips out once the dancing starts, when nobody's watching closely enough to ask where she's going.
She knows exactly where she's going. Senku isn't at the party. Senku is never at the party, not really, not when there's an excuse not to be, and tonight the excuse is some recalibration he wants to run himself before the launch window narrows any further. She tells herself she's bringing him food. She's holding a plate of something Francois made, and it's a perfectly reasonable errand, and she's not thinking at all about the fact that this is the first time in weeks she'll have him entirely to herself, without Xeno's dry commentary or Chrome underfoot.
The lab is dim except for the working light over Medusa's console, and Senku doesn't look up when she comes in. He's murmuring readings to himself the way he does, half a conversation with no one, and Luna stands in the doorway a moment just watching the back of his neck, the line of concentration in his shoulders, before she remembers she's holding a plate.
"You didn't come," she says, too brightly, closing the distance before she's decided to. "Everyone's asking."
"Nobody's asking." He doesn't turn. "This calibration's got maybe four minutes left before the values lock, and if I want good data I gotta not talk to anyone until then."
"I brought food."
"Put it down anywhere."
She should put it down anywhere. Instead she comes around to his side of the console, closer than the errand requires, and it's only once she's there, close enough to see the numbers scrolling, close enough to smell the ozone-and-machine-oil smell that's somehow become one of her favourite smells in this ridiculous stone world, that she registers how still she's supposed to be standing and how little she's managing it.
"Four minutes," she repeats, mostly to have something to say. "You could've come for four minutes at the start. Danced with me for four minutes?"
"Luna."
"I'm just saying it wouldn't have killed the whole timeline."
"Luna, don't—"
She doesn't know, later, whether it's her hand on his arm or the plate tilting or just the fact of her voice pitched low and close to his ear that does it, the Medusa's array is tuned finer than either of them accounts for in the moment, sensitive at exactly the fold in the sequence where interference does the most damage, and a warm body leaning in unplanned, murmuring something not meant for a machine to parse, reads as input all the same. Not sabotage. Just noise where there should have been none.
The console shrieks a fault tone half a second too late for either of them to do anything about it.
Senku's already moving before Luna understands what the sound means, shoving back from the console toward the containment cell, and she follows two steps behind, plate abandoned somewhere on the floor, her stomach dropping before her mind catches up to why.
A shape begins to form in the air where they were, a human shape, details appear, a shoulder, a jaw. A head of hair so aggressively familiar that Luna's first coherent thought is that she's finally, actually, going insane.
The second Senku opens his eyes at the same moment the first one goes rigid beside her, and for a second the two of them: the blinking, newly-assembled one and the harried, dishevelled original, just stare at each other like the universe has made a joke neither of them finds funny.
“A second me! This is exhilarating!” says Senku-1.
And then Senku-2 chimes in. “Get excited!”
Senku-1 and Senku-2 step forward at the same moment but Senku-2 stops at his first step, his expression changes.
“Huh.” His knees buckle.
Luna catches his arm before his head can hit the console.
"Sit down," she instructs, already reaching, already thinking in the shape her body knows better than her head ever has: pulse, colour, breathing, the things she can check with her hands instead of theory. "Now, before you go down on your own."
Senku-1 opens his mouth probably to argue, probably to demand data first, that's always his instinct, but Senku-2's newly-formed legs are not holding and practicality wins over curiosity for once. Between the two of them they get Senku-2 seated against one of the walls, and Luna crouches in front of him, two fingers at his wrist, counting.
"Fast," she murmurs. "Not dangerous-fast. Just new."
"Obviously." Senku-2's voice comes out shaky, but the dryness is already there, already fully formed, like sarcasm was in the blueprint from the start. "Everything in me is new. Ten million percent unprecedented."
"Don't talk yet."
"I can talk fine." He looks at her, looks at her properly, the way Senku-1 looked at her the first time they met, back in California, and hadn't ever since. Except there's nothing careful about it yet, nothing filed away behind years of deciding what's worth saying out loud. "You're the one who was standing too close to me before this happened."
Luna's fingers still on his pulse.
"That's not … that's not relevant right now."
"Felt relevant to me." Senku-2 tips his head slightly, studying her the way you'd study a result you hadn't expected but weren't unhappy about either. "I've got his memories up to about four seconds before the fault. You had your hand on his arm. You said something about dancing." A pause, clinical and devastating in the same breath. "He wanted you to stay there longer. I can tell, because I still want it, and we're presumably running the same hardware."
"Oi." Senku-1's voice cracks in sharp, too sharp, a hand landing on the clone's shoulder like he can physically stop the sentence from finishing. "You don't get to just say that."
"Why not? It's true. You'd just spend another four hours deciding whether it was worth saying, and by then she'll have gone back to the party." The clone's gaze doesn't leave Luna's face. "I don't have four hours of pride left to burn through yet. Efficient, really."
Luna's still holding his wrist. She realises, distantly, that her other hand has found the original's, steadying him too, an old habit, the same hands-on instinct that developed tending Senku through his gunshot wound, and now she's crouched between both of them, tethered to two versions of the same impossible, infuriating, unbearably specific men.
"This is insane," she says, mostly to herself.
"Ten million percent," Senku-2 agrees, and behind her, quiet, furious, cornered by his own unfiltered mouth, the original doesn't disagree either.
Senku-2's eyes wander and Luna knows he's tracing out her body. "Nature builds things efficient when they're built right. Nautilus shells, galaxies, you. Some proportions just work without trying.”
Luna flushes bright red and Senku-1 makes a sound, half protest, half something else entirely, and Luna feels his hand tighten in hers where she's still holding it. The clone's words hang in the air between them, heavy and undeniable, and when Luna looks back at the original, his eyes are fixed on her with an intensity that makes her breath catch.
"You're not helping," Senku-1 says to his double, but his voice has gone rough, stripped of its usual scientific distance.
"I'm helping significantly more than you are," Senku-2 replies, and then his free hand, because she's still holding his wrist, still counting his pulse like it matters, reaches up to touch her face. His fingers are warm, newly-made, tracing the heat in her cheeks with clinical fascination that dissolves into something hungrier as he learns the shape of her jaw. "You're warm here. Capillary response. Sympathetic nervous system activation."
"Stop analyzing me," Luna breathes, but she doesn't pull away.
"I can't. It's what I am." His thumb brushes her lower lip, and she parts it without meaning to, instinct overriding intention. "But I can do other things simultaneously. Multitasking."
Senku-1 shifts behind her, close enough now that she can feel his breath against her hair, feel the tension radiating off him in waves. "The calibration's ruined anyway," he says, almost to himself. "Four minutes, eight minutes, the window's blown regardless."
"Then we have time," Senku-2 stated, and it's not a question.
Luna turns her head to look at the original, to find some anchor in his expression, but what she finds is worse, or better. His glasses are slightly askew, his hair mussed from running his hands through it, his pupils blown wide and dark. He looks like he does when he's on the verge of a breakthrough, except the breakthrough is her, them, this impossible geometry of want.
"Say something scientific," she whispers, desperate for the familiar ground.
"Sympathetic arousal," Senku-1 murmurs, his hand finally moving from her shoulder to her waist, settling there with a familiarity that makes her gasp. "Mirror neurons. Watching him touch you activates the same neural pathways as touching you myself. I can feel what he's feeling. I remember wanting to, and now I watch myself doing it, and the feedback loop is…" He breaks off, jaw tight. "Ten billion percent overwhelming."
Senku-2's hand slides from her face to her throat, thumb resting against her pulse point where she was checking his. "Elevated heart rate. One-twenty. One-thirty." His other hand finds her free one, guides it to his chest, pressing her palm against bare skin where his shirt has come open. "Feel that? New heart. First time beating this fast. First time for everything."
Luna can feel it beating wild and rapid beneath her palm, and behind her Senku-1 presses closer, his own chest against her back, and she can feel his heart too, matching rhythm, two drums beating out the same desperate tempo.
"Experiment," Senku-1 breathes against her ear, and she feels him hard against her hip, feels the last of his restraint fraying. "We need to establish parameters. Control variables."
"Fuck parameters," Senku-2 says, and leans in to kiss her.
It's different from anything she's imagined, more desperate, more curious, his mouth tasting of ozone and newness and something uniquely Senku that makes her dizzy. He kisses like he's gathering data and losing himself in it simultaneously, his tongue sliding against hers with experimental pressure that quickly finds what makes her moan and repeats it, optimises it, perfects it in seconds because he has the blueprint and the motivation.
Behind her, Senku-1 makes a broken sound, and then his mouth is on her neck, teeth grazing the tendon there with just enough pressure to arch her back, press her harder against him. His hands move with scientific precision, unbuttoning her dress at the back, mapping the skin he reveals with spreading fingers, noting every gasp and shiver with murmured observations that dissolve into curses when Senku-2's hand slides down to cup her breast through the fabric.
"Response curve," Senku-2 mutters against her mouth, thumb circling her nipple through the cloth, finding it hard and sensitive. "Highly reactive. He never touched you here, did he? Wasted data."
Senku-1's hand is already sliding around to replace his double's, larger and more certain, palming her with a familiarity that makes her cry out into Senku-2's mouth. "Don't talk about me like I'm not here."
"Then be here," Senku-2 challenges, breaking the kiss to look at his original with eyes that hold no patience, no pride, only naked want. "Stop watching and participate. I know you want to. I want to. We're the same person - if I want her this badly, so do you."
Senku-1's hand stills on her breast, and for a terrible moment Luna thinks he'll pull away, retreat into analysis and safety. But then his other hand is tilting her head back, turning her face toward his, and he's kissing her with all the pent-up precision he's been hoarding for months, deep and thorough and devastatingly methodical, his tongue finding exactly where she likes it, his teeth grazing her lip with calculated pressure that makes her knees weak.
"Better," Senku-2 approves, and then his mouth is on her neck from the other side, opposite his original, and Luna is caught between them, surrounded by the smell of ozone and machine oil and something darker, muskier, male. Two mouths on her throat, two sets of hands, both certain, both curious, unfastening her dress, sliding beneath the fabric, mapping her body with shared intent.
They work in tandem without speaking, Senku-1's hands finding the catches of her undergarments while Senku-2's trace patterns on her skin, noting reactions, optimizing touch. When her dress falls open, Senku-2 pulls back to look at her with undisguised hunger.
"Optimal," he murmurs, and the word should be clinical but it sounds like worship. "The proportions I mentioned. Efficient design."
"Stop talking," Luna manages, but she's smiling, flushed, reaching for him.
"I can't, I'm new. Everything's words and sensation and I need to name it or I'll drown." He catches her hand, brings it to his mouth, kisses her palm with lips that are already learning gentleness. "You're beautiful. I have his memories of thinking you were beautiful, but it's different from inside. From this close."
Senku-1's arms tighten around her waist, pulling her back against him, and she can feel how hard he is now, straining against his trousers, no longer hiding it. "We should move," he says, voice rough. "The cot. The floor. Somewhere I can—" He breaks off, pressing his face into her hair. "I need to be inside you. Both of us. I need to know what that feels like."
"Comparative analysis," Senku-2 agrees, already helping her step out of the pooled fabric of her dress, his hands steadying her when she wobbles. "Same genetic material, different experiential variables. Which one of us makes her respond more intensely?"
"Neither," Luna says, finding her voice, her boldness rising to match theirs. "Both. I want both."
They move to the cot together, a tangle of limbs and shedding clothes. Senku-1 spreads his lab coat over the rough blankets in a concession to comfort; and then they're guiding her down, two pairs of hands arranging her like a precious instrument, positioning her with care that quickly becomes less careful as need overtakes precision.
Senku-2 kneels between her legs first, his eyes dark as he looks down at her, naked and open and waiting. He's shed his shirt, and his body is Senku's body exactly. But his expression is different, hungrier, less guarded.
"First time," he says, almost wonderingly, and then he leans down to kiss her stomach, her hip, the inside of her thigh. His breath is hot against her most sensitive skin. "First time for everything."
"Wait—" Senku-1 starts, but Luna reaches up to pull him down beside her, capturing his mouth in a kiss that tastes of urgency and surrender.
"Let him," she breathes against his lips. "Let me feel you both."
Senku-2 doesn't wait for further permission. His mouth finds her, tongue sliding through her folds with experimental curiosity that quickly becomes focused intent as she cries out, her hips bucking against his face. He learns her in seconds, where to press, where to circle, where to suck, and the precision is devastating, calculated to bring her to the edge with ruthless efficiency.
"Fascinating," Senku-1 murmurs, watching his double work her, his hand sliding down his own body to grip himself through his trousers. "The response curve, he's found the optimal rhythm already. I can see it in her breathing, her muscle tension—"
"Stop watching!" Luna gasps, reaching for him, pulling at his clothes until he helps her, shedding shirt and trousers until he's as naked as she is, as naked as the man between her legs who is making her see stars with every flick of his tongue.
Senku-1 stretches out beside her, his hand replacing his double's mouth when Senku-2 pulls back to breathe, to observe, to note her reactions with eyes that are glazed with his own arousal. Two fingers slide into her easily - she's wet, so wet, ready for them both - and Senku-1 crooks them exactly right, finding the spot that makes her back arch off the cot.
"Here," he says, clinical even now, pressing again, making her moan. "Prostate equivalent. Maximum nerve density. He found it too, didn't he?"
"Yes," she manages, "yes, both of you, please, please …"
Senku-2 moves up her body, kissing his way north, pausing at her hip, her stomach, her breast, capturing her nipple in his mouth and sucking hard while his original continues to work her with fingers that know exactly how to curl, exactly how to press. Luna is overwhelmed, sensation coming from every direction, two men who share a mind focused entirely on her pleasure.
"Now," Senku-2 says against her breast, looking up at his original with a challenge in his eyes. "Which of us? Or both?"
"Both," Senku-1 says, the word torn from him, and he withdraws his fingers, making her whimper at the loss, only to replace them with something larger, hotter, himself, positioning himself at her entrance with a trembling hand. "But I need, Luna, I need to feel you first. Just once, just to know"
"Yes," she breathes, reaching up to frame his face, to pull him down to her. "Yes, Senku, please—"
He pushes into her slowly, carefully, the way he does everything, but the control is costing him, she can see it in the tightness of his jaw, the sweat on his forehead. He fills her inch by inch, stretching her, and when he's fully seated they both gasp, foreheads touching, breathing each other's air.
"Data," he whispers, but it sounds like prayer. "Oh god, Luna, the data is excellent. "
"Move," she begs, rocking her hips against him. "Please, move!"
He does, setting a rhythm that's experimental at first, testing angles and depths, but quickly becomes driven as she responds, as her nails dig into his back, as her legs wrap around his waist to pull him deeper. Senku-2 watches them with dark eyes, his hand moving on himself in time with his original's thrusts, learning from every gasp Luna makes, every shudder that runs through her.
"Faster," Senku-2 instructs, and Senku-1 obeys, snapping his hips harder, making her cry out. "There. She likes that depth. The angle, tilt her hips!"
Senku-1 does, adjusting without question, and Luna moans as he hits exactly the right spot, pleasure building sharp and urgent in her belly.
"Close," she manages, "I'm close, don't stop!"
"Don't stop," Senku-2 agrees, and then he's moving, positioning himself beside her head, guiding her to turn her face toward him. "Here. Taste yourself. Taste us."
She opens for him eagerly, taking him into her mouth as Senku-1 continues to drive into her, the dual sensation, being filled, being used, being worshipped by two versions of the same impossible man, pushing her rapidly toward the edge. Senku-2 tastes like salt and newness, his hips moving carefully, testing her limits, while his original loses rhythm above her, chasing his own release.
"Together," Senku-2 gasps, his hand finding hers where it grips the cot, threading their fingers together. "We should come together. Sympathetic response. Mirror neurons…"
"Shut up," Senku-1 groans, but he's smiling, wild and undone, looking down at her with an expression that's pure feeling, pure Senku stripped of all defense. "Luna, Luna, Luna!"
She comes first, the pleasure cresting and breaking over her in waves that start where Senku-1 fills her and radiate outward, making her cry out around Senku-2, making her body tighten and shudder. The contractions trigger Senku-1's own release, he buries himself deep with a shout that sounds like her name, spilling into her with abandon.
Senku-2 follows seconds later, his hand tightening in hers as he pulses in her mouth, groaning something that might be data or might be devotion, his hips jerking through the aftershocks as she swallows him down.
They collapse together, a tangle of limbs and lab coats and sweat, the laboratory smelling of sex and ozone and victory. Senku-1 withdraws carefully, gathering her against his chest, while Senku-2 stretches out on her other side, his hand finding her hip, her waist, touching her like he still can't believe she's real.
"Conclusion?" Senku-1 breathes against her hair, his heart still pounding against her back.
"Highly successful," Senku-2 answers, pressing a kiss to her shoulder. "Replicable."
"Replication needs testing," Luna corrects, turning her head to kiss him, then turning further to kiss the original, tasting herself on both their mouths. "Definitely needs."
Outside, the party continues, Ryusui's laughter carrying across half the town. Inside the lab, three hearts beat in synchrony, and the Medusa console hums quietly in the background, already beginning its next calibration cycle.