Archive of Our Own

Despite Gen’s numerous comments about desiring a harem of cute girls, his bisexuality had always steered him towards partners on the more masculine end of the spectrum.

To be fair, women were nice enough and he could appreciate their softness and sweetness the way he appreciated the occasional cocktail. He enjoyed flirting with them and often encouraged their attention, especially considering how they made up the majority of his fan-base, but it almost always stayed surface level and casual. On the flip side, his relationships with men had been few and due to the nature of his profession had operated in secrecy, but there was a common trend amongst them.

Gen liked men who could be a little rough with him. Men who made him feel more delicate in comparison - set his heart racing and stomach fluttering. Someone who could take care of him, pamper him, be a little bit obsessed with him.

He liked deep voices and athletic builds, handsome smiles and charming looks.

In short, the exact opposite of Senku.

Which was probably why he’d been caught so completely off guard by him.

—

1

“I told you I’m busy,” Senku grunted, not looking away from what he was doing even as Gen clicked his tongue disapprovingly.

“You’ve been usy-bay for two days now, this can’t wait any longer.”

Senku snorted but didn’t dignify him with a further response. 

Gen scowled, his careful composure finally fractured after several days of frustration. He’d chased the other man around to try and feed him and get him to sleep in more than short burst power naps to no avail. He’d spent hours trying to get clarification on upcoming steps between diffusing murmurs of discontent and distrust amongst the villagers who were similarly confused about what they were being asked to do only to be brushed off or given a quick shot lecture that left him with more questions than he’d started with.

And now that he’d finally cornered him, he was not backing down.

“Senku-chan, I really need you to-“

His words cut off by the sudden and loud crack of glass, sharp like a gun shot, followed by a flash of light and heat.

Gen didn’t have time to register it before a hand grabbed him by the front of his yukata, wrenching him to the side and twisting him in a graceless, stumbling twirl to the ground. Grunting at the impact, Gen winced against the acrid smell permeating the air as well as the sound of fragments hitting the dirt around him like hail, ears ringing and head foggy.

When he managed to open his eyes, he was surprised to find Senku crouched over him, one arm held up to shield himself from the onslaught as he surveyed the damage behind them. Gen stared, half dazed, at the other man’s profile, back lit by the sunlight drifting through the doorway and the fog of quickly dissipating smoke. There was ash and shards of glass in his hair and a new scorch mark across the shoulder of his coat, but Gen was more surprised by how solid the other man felt on top of him.

He hadn’t touched Senku much since his arrival to the village, but in that baggy science dress of his he’d always seemed small and wiry. He was dwarfed by men like Kinro and Magma, and even Chrome was seemingly more fleshed out than the modern scientist.

Hell, Kohaku’s shoulders were wider than Senku’s.

But with knees bracketing his hips and one arm braced next to Gen’s head, the lean muscles of his forearm and tricep tensed, Gen realized Senku was surprisingly sturdy for a bean pole.

His observation was cut off when Senku lowered his other arm, turning to look down at him and revealing a cut slowly oozing blood from the high point of his cheek. Red eyes scanned over him quickly, wide and concerned and Gen was momentarily dumbstruck by just how pretty they looked in the low light, only for them to harden in irritation.

“You idiot, are you trying to get yourself killed?” 

Gen blinked up at him, brain still struggling to catch up. For a moment, all he could focus on was the weight pressing him into the ground, solid and unyielding, and the heat radiating through the thin layers of fabric between them.

When he didn’t react right away, Senku frowned, leaning down to look at him closer, “Did you hit your head?”

“No, no, I’m ine-fay!” Gen answered immediately, willing his voice forward with brute force as Senku drew closer. “Just admiring the view, Senku-chan~”

It came out lighter than he felt, habitual almost, but it worked exactly as Gen intended to distract the other man.

Senku snorted, leaning back with a roll of his eyes, “Definitely hit your head if you’re saying stupid shit like that…”

Pushing to his feet, Senku offered a hand to help him up and Gen took it without a thought. Senku’s grip was firm, stronger than he expected, hauling Gen to his feet in one clean motion.

Before he had a chance to react, Senku’s free hand was on his face, tilting his chin up to angle him towards the light. Red eyes narrowed as he scanned him over for signs of injury, and Gen hoped he was too focused on his task to notice the way Gen’s breath had hitched at the contact.

“Pupils reacting normally… balance seems okay…”

His voice was low, more a rumble than a mutter, tilting Gen’s head this way and that way just a little too roughly.

For a brief moment Gen felt something swoop down low in his belly at the idea of those hands on the back of his head instead, fingers threaded through his hair and pushing-

“You’re bleeding,” he blurted out, stepping back as heat flared up his neck. “I’ll go get Chrome-chan so we can start cleaning this up.”

Senku blinked, absently reaching up to the cut on his face, still slowly oozing, giving Gen a chance to scamper over the shards of glass to the door. “Yeah, yeah if by we you mean me and Chrome… Grab Ruri while you’re at it in case this needs stitches.”

Gen paused in the doorway, fingers curling slightly around the wood, watching as Senku began sifting through the wreckage as if the near-explosion had been nothing more than a minor inconvenience. As if yanking Gen out of danger, pinning him to the ground, and shielding him with his body had been a blip in his day and not something notable.

It was far more irritating than it should’ve been and Gen found himself huffing as he slipped out the door to fetch Chrome and Ruri.

—

2

Gen hated getting sick and in the modern age he had gone to extreme lengths to avoid it. Taking a wide variety of daily vitamins and supplements, avoiding crowds, slathering himself in hand sanitizer regularly - he was proud to say he hadn’t had so much as a sniffle in nearly three years before petrification.

“I’m dying,” he whined, voice thick with congestion and raspy from the soreness of his throat.

“Stop being a drama queen,” Senku snorted, stirring some random powder into a tea cup. “It’s a cold, not cancer.”

Gen made a pitiful sound, wriggling until one of his feet escaped the blankets, shifted off the bedroll like a tragic figure in a Renaissance painting. 

A hand smacked his ankle back under the blanket. 

“I’m hot,” he complained, trying to push it back out only for a firm grip to settle on his shin.

“That’s the fever,” Senku replied flatly. “Guarantee you’ll be freezing in the next few minutes.”

“So I’ll get back under the blankets then.” 

Senku rolled his eyes, “Sit up and drink this,”

He didn’t wait, taking hold of Gen’s shoulder to jerk him up to sitting. Gen groaned as the motion made his head swim, falling limply against Senku’s side and wrinkling his nose when the cup was placed in front of him.

Even through the stuffiness of his sinuses Gen could tell it smelled medicinal - bitter and pungent in a way that made him want to recoil. Unfortunately, Senku held him firmly in place.

“This’ll help with your fever while we finish the next batch of sulfa drugs.”

Gen turned his head away petulantly, “Smells like something you scraped off a tree.”

“That’s exactly what happened. I put some willow bark in here to help you sleep,” he nudged the rim of the cup closer to Gen’s mouth. “Drink it.”

Grunting his disapproval, Gen attempted to sink bonelessly further against Senku in protest - as if becoming dead weight would somehow make Senku give up. 

The scientist huffed, adjusting his position, “You are such a pain…”

Gen didn’t have a chance to respond, Senku’s grip on his arm shifting to loop around his shoulders, reaching just far enough to cup his jaw in a surprisingly large hand.

He could feel the callouses of Senku’s palm against his chin as his head was tilted back, breath hitching when he found Senku right there, face so close to his he could count his (ridiculously thick) eyelashes if he wanted to. His pulse jumped at the realization that Senku wasn’t looking at his eyes but at his mouth, gaze intent and focused in a way that sent a fluttering in his stomach and had him licking his lips instinctively.

“Open your mouth.”

It was less of a request and more of an order, firm and decisive, and Gen’s breath hitched when Senku’s thumb pressed just under his lip, mouth going slack at the first nudge.

Which he immediately regretted when Senku tipped the foul tasting medicine into his mouth and forced it shut so he had to swallow.

“See?” Senku smirked victoriously, “not dead.”

Gen made an affronted noise, wriggling his head to escape. He froze when Senku’s other hand reached up, palm brushing over his cheek and temple to push his hair out of his face.

It was subtle, but unmistakable how his fingers lingered before pressing more deliberately against Gen’s skin, hot from more than just the fever as a flush raced up the back of his neck. He could feel the exact moment Senku switched from smug amusement to problem solving mode, palm settling on his forehead in a way that fortunately blocked Gen’s line of sight and gave him a moment to try and calm his racing heart.

“Damn, your fever’s climbing faster than I thought…”

Gen swallowed over the suddenly dry feeling in his throat, acutely aware of how close they still were. His side was pressed flush to Senku's chest, practically perched in the other man's lap, and for one ridiculous moment he hoped his fever sweats hadn't made him smell.

“Take off your pants.”

“…excuse me?”

Senku had begun untying the obi around his waist, fingers sure and determined as he shoved Gen's haori and yukata top down his arms. “I need to cool you down before your temperature spikes any higher. Pants.”

There it was again - that blunt, commanding tone - like the answer was obvious and Gen was an idiot for not already complying. 

It shouldn’t have done anything to him. 

Which was why it was so concerning that it really really was.

“If you wanted to get me naked there are easier ways,” he croaked, trying for levity despite the heat suffusing his face as he reached for his waistband.

Senku didn’t even dignify him by looking up. “You’re overheating. We need to get it under control before you start frying the few brain cells you still have.”

Gen opened his mouth to snap back only to promptly forget how words worked when Senku’s fingers brushed his hip. It wasn’t even close to what one would consider a caress, far too clinical and impersonal a touch as Senku efficiently maneuvered him, and yet it set his nerves on fire and sent shivers racing up his spine.

Cursing internally, Gen tried to steady his pulse. He was being ridiculous, his illness obviously compromising his cognition because there was no other explanation for how he was reacting to Senku of all people.

Stringy, science gremlin Senku. Who thought regular sleep and meals were beneath him and considered reconstructing generators to be a relaxing activity. The man whose bedside manner amounted to “don’t let them die” and nothing more.

But as the other man continued to flit around him, muttering to himself and maneuvering Gen as he needed, Gen found himself entranced.

Decisive, certain, assured. Each movement precise as if he had already mapped out every step, every contingency. No fumbling, no second guessing, just action - confident and resolute.

Each command given with the expectation that Gen would listen - not because Senku threatened or cajoled, but because he knew he was right and he knew what he was doing. 

Confident that Gen would obey.

Gen prided himself on control. He was a master at reading and steering situations, dancing circles around expectations and manipulating outcomes in his favor without anyone noticing he’d done anything at all. He was always the one pulling the strings, even when it looked like he wasn’t.

But in that moment, half-dressed and feverish while Senku barked orders and adjusted him to his liking, tucking him onto the bedroll and setting a cool cloth to his forehead, Gen wasn’t in control at all.

And worse -

A shiver ran through him that had nothing to do with the fever.

He didn’t want to be.

–

3

As a skilled magician and mentalist, Gen had always had a habit of observing other people’s hands. They could tell a lot about a person - what they did for work or in their spare time, places they’d been or activities they had done recently. 

Chrome’s hands were sturdy and strong, almost always smudged with dirt at least somewhere, with a tendency to tap his fingers on random surfaces.

Kohaku’s fingers were long, the knuckles dark from years of training and fighting, with well earned callouses lining the palms and scars striping the skin while Ruri’s were soft and dainty, fingernails well kept and skin unblemished from years spent in quarantine. 

Kaseki’s were worn and wrinkled but tough, permanently stained from years of crafting and weathered from countless hours by the forge while Suika’s were the small, chubby fingers of a child, tinted with whatever fruit or berry she had come across during the day.

He contemplated his own hands, frowning at the dryness of his cuticles

“Outta the way, Mentalist.”

Gen gave a startled yip when warm hands encircled his waist, shoving him to the side like a pesky piece of furniture. He stumbled half a step, catching himself on instinct more than balance, any further protest dying in his throat when the hands didn’t move away.

Senku peered past him at whatever random thing he was looking for on the shelves, seemingly unbothered by the fact that he was still holding Gen in place.

For how attune to people’s hands as Gen was, it had never occurred to him just how… big Senku’s were. He’d always been more focused on just how busy they always were, how capable. Hands that had been refreshed by petrification only to immediately be put to use, showing the undeniable signs of hard work despite their owner’s slight build and lack of physicality.

His fingers were long and thick, practically overlapping where they rested above Gen’s navel, one absently tapping against the flat plane of Gen’s stomach as he muttered to himself. Gen swallowed, very carefully not moving, even when one of Senku’s hands flexed against him as he leaned further forward. Firm fingertips pressing through fabric with a casual strength, the heel of Senku’s palm resting just above the curve of his hip like it belonged there - warm and steady.

It should not have been as distracting as it was.

Senku clicked his tongue, reaching up to move a few of the jars out of the way, still searching for whatever he had come for, and Gen found himself staring at the outstretched limb.

Senku’s hands were calloused - a faint roughness along the fingertips and palm. Not the same as Kaseki’s forge-worn hands or Kohaku’s battle-earned grip, but something else entirely. His hands were those of a builder, a creator, a mind that never stopped long enough for softness to matter.

“There it is,” Senku muttered, finally pulling a jar from the back of the shelf. To Gen it was indistinguishable from several in its vicinity, but he knew better than to comment on that fact.

Letting out a breath he hadn’t realized he was holding, Gen shifted his weight as Senku finally straightened up. The hand lingering at his waist didn’t immediately disappear, instead giving two firm pats to the curve of his hip the way one would to a machine that had finally cooperated.

Every tangible thought in Gen’s head evaporated and he stood frozen in place even as Senku stepped away from him, attention turned to the jar in his hands.

“…you good?” Senku asked and Gen made the mistake of looking at him at the exact moment he took hold of the lid and twisted it off. Veins bulged on the back of his hand, muscles in his forearm tensed, and it popped off with a satisfying sound.

“…mm-hmm,” he managed finally, high in the back of his throat, whipping back around to the shelves though unable to even begin to recall what he’d been there for in the first place.

Senku made a sound of acknowledgement, clearly not paying any sort of actual attention, already moving on with his prize, “Then get moving, we’ve got too much shit to do for you to hide in the storeroom all day.”

And with that Gen was alone. He took several deep breaths, eyes closed and forehead dropped to the shelf in front of him, trying desperately not to think about the last few minutes.

How Senku had moved him so easily, how secure his hold had felt, how dexterous those fingers probably were…

“Ohhhhh I’m in trouble,” he breathed. 

—

4

It had been no secret that Gen liked being rewarded and praised. No one sought out fame without being somewhat of an attention whore and Gen had been no different. Even as his time in the Kingdom of Science pivoted the praise from the roaring applause of a crowd to a more subdued satisfaction in a job well done, Gen still relished each compliment he got.

And if he was more affected by the praise of a certain scientist, no one had to know about it.

Gen tried to convince himself it was because Senku’s praise was hard won - very little seemed to impress him and he was not the sort of man to dole out compliments easily. It wasn’t that he wasn’t appreciative - Senku was very open with his thanks, often with the clap of a shoulder or a high five with a standard “good job” - but he was the sort that thought doing what was asked of you was baseline and not worthy of extra accolade. 

So when Senku held out a small box to him, he didn’t know what to do at first.

“Still a few weeks out from what I need for more cola, but figured this’ll make up for the bat shit.”

When the lid came off Gen found himself blinking down at a stack of playing cards.

A joker sat right at the top, the art simple but clean - similar to the doodles he’d seen scrawled on the margins of Senku’s notes and plans - in a familiar outfit with perfectly drawn petrification scars running down their cheeks. 

“Did you… make these?” He found himself asking, voice softer than usual - too distracted to put any sort of act into it. “For me?”

Senku snorted, pinky finding its way into his ear, “No, I made ‘em for Taiju - he’s real into black jack.”

Gen pulled the deck free, fanning them out and looking at each carefully constructed card. The paper was thick - still flexible like a playing card should be but not flimsy. Each suit was hand drawn, the color of the ink stark against the off-white background, with little touches that screamed Senku.

Familiar faces on the high cards - Senku, Kohaku, Chrome, each suit holding a different item in their mirrored hands. The symbols on the numbered cards almost too perfect, as if they’d been stamped, but there was an added detail of additional pips like the faces of a die in each tiny shape. 

“This must’ve taken weeks…”

“Had some time between tasks, no big deal,” Senku shrugged. “Consider it a late birthday gift.”

Gen paused, “I didn’t tell you my birthday. Didn’t even give you a math problem to solve to figure it out.”

Glancing up, Gen was surprised to see Senku looking a little… embarrassed. It was a new expression, lips pursed and jaw tight, pointedly not looking at him and pinky digging in his ear far more aggressively than it usually did.

“Yuzuriha knew it, she was a big fan back before.” There was a beat and red eyes darted over to him, an amused smirk tilting up the corner of his mouth. “You would be an April Fool’s baby, wouldn’t you?”

Gen clicked his tongue automatically, the response instinctual after years of interviews despite the warm feeling spreading through his chest. 

“Hmm, a tragic tale, really,” he drawled, shifting the cards between his hands in an effortless waterfall flourish. “Destined from birth to be a man no one would ever believe.”

“Yeah, yeah,” Senku waved him off, but there was a flicker of satisfaction in his eye as he watched Gen manipulate the cards. “Don’t be going all soap opera on me. You like ‘em or what?”

Gen turned the cards over once more, looking at the backs. The purple color was more periwinkle than lavender, and the lettering more clearly a stamp application. Looking closely, he could see small patterns in the print - the phases of the moon in a simple Selene-o-gram repeating down the back with the Kingdom of Science rocket ship symbol in the middle. It was subtle, barely a variation in color at all unless you were really focusing, but the extra detail was just another sign of the obvious effort that had gone into the gift.

Hours upon hours of work - designing, formulating ink, carving stamps, making and cutting paper, and all the adjustments and trials that had to have gone into each aspect. All done while juggling a million other responsibilities and an incoming war. Forging alliances, creating impossible inventions, too many sleepless nights to count and Senku had still made time for something as frivolous as a deck of playing cards.

Gen raised his eyes to Senku, the scientist looking down where Gen was still absently shuffling the deck with an assessing eye - no doubt cataloging the way the cards shifted over one another and making notes for improvements for next time.

And that’s what really hit Gen, the immediate certainty that the gift hadn’t been a one off. That if he asked, Senku would absolutely make him another set - maybe with a snarky comment or complaint, but it would happen.

It would have been easy for Gen to slip into a performance. Flash a grin and toss out something dramatic - something sure to make Senku snort and roll his eyes, maybe laugh if Gen was really lucky - it was what he did best, after all.

“…You’re ridiculous,” was what he found himself saying instead, voice uncharacteristically soft. “This…” his thumb brushed over the joker once more, nail tracing over the carefully drawn petrification scar, “it’s way beyond what I deserve, you know.”

Senku’s brow twitched, immediate and irritated, “Don’t be a dumbass.”

He turned away, as if the conversation was already over, and Gen flipped the cards over in his hands again. Not a flourishing shuffle or energetic fan, no performance, just looking at them.

If asked, very few people would describe Senku as nice. Other words came to mind - sarcastic, pragmatic, hard-working - but Senku wasn’t nice.

Senku was efficient and oftentimes blunt, he didn’t waste time on flowery words or tip toeing around things. He could be rude and acerbic, short and dismissive, demanding and exacting.

But every so often he would do something so quietly deliberate that it made the rest of it irrelevant.

Making cotton candy under the guise of testing science equipment, lighting up a tree on Christmas Eve as if it were any other day in the dead of winter, making and storing spare lenses in case a melon helmet met an untimely demise and needed immediate repair.

All of those gestures had some sort of logical reasoning behind it, some sort of utility he could hide behind to disguise the softness.

A deck of cards, though, was entirely frivolous, and yet Senku had still gone through the effort to make it. A quiet indulgence in a world that did not often allow for them, something specifically for Gen.

He had never received a more thoughtful gift in his life. 

And that was the crux of it - Senku wasn’t nice, but he was kind.

He cared.

Gen didn’t say anything for a long moment, not because he was lost for words, but because he was trying to pick something to say that wouldn’t make the moment heavier than it needed to be.

Senku had already moved on in the way he usually did, attention half on Gen and half somewhere else entirely. Mentally checking down a list of whatever task or problem needed to be addressed next, never still for longer than necessary if he could help it.

He cleared his throat, fanning the cards in an effortless and familiar flick of his wrist. “Well, thank you, Senku-chan, it’s onderful-way to have some of my tricks of the trade again. And so beautifully made, too!”

Senku huffed, clearly relieved by the pivot in tone, even if the edges of it seemed… softer.

“Yeah, yeah, don’t mention it…”

Gen smiled, the expression easy and genuine in a way that didn’t quite feel as performative as usual, fingers lingering on the cards for just a second longer than necessary as he tucked them into his sleeve.

—

5

Gen had always been aware of himself. Not in the vague, philosophical sense people liked to pretend at, but in the precise, almost surgical way of a craftsman studying his own tools. He’d learned to master his smiles, calculate every pause and tilt of his head, carefully consider every word - perfectly tailored to his audience and what they wanted to see.

People were far easier to work with when you gave them what they wanted.

It had kept him fed, kept him safe, kept him valuable. It was a skill that was as natural to him as breathing, and so it never stopped.

Not when the world ended. Not when it restarted. Not when he finally defected fully to the Kingdom of Science.

The show, as they said, had to go on.

It wasn’t a grand incident that had drawn his attention to it, no loud faux pas he couldn’t recover from, but instead the silences. Not the awkward ones that people rushed to fill - the ones marked by the sound of breathing and tapping feet, anxious fidgets and noise made just for the sake of it. But the comfortable ones. The ones that stretched on without snapping.

He found himself gravitating toward Senku more often. Not because he had to - honestly it would’ve been easier to dodge work if he’d avoided the other man - or because there was some strategic benefit to it, but because it was… easy.

Gen stopped trying to fill every gap in the conversation. Stopped calculating every reaction. Stopped - just a little - being on all the time.

He stopped exaggerating his reactions - his gasps smaller, his compliments less syrupy, sometimes he didn’t react at all. Watched Senku work and waited for his reaction.

Except Senku didn’t react. He didn’t look disappointed or lose interest, didn’t seem to even notice at all. He kept talking to Gen the way he always did - matter-of-fact, a little too fast when he was excited, and dropping explanations mid-sentence only to pick them up three topics later. He gave him tasks and ordered him around, always blindly trusting that whatever he’d asked for would get done.

No expectation of performance, no demand for simpering or charm, no need for entertainment.

And at first it had been unnerving. Gen had to fight the natural urge to fill the silences, to prove he was engaged and if not understanding what Senku was saying at least able to make a joke about it. 

But slowly he realized that even when he stayed quiet, Senku didn’t seem to care.

He showed no subtle cues of boredom, no irritation or shift in tone to draw him back in, utterly unconcerned as if Gen’s silence was simply another state of being and not something that needed to be corrected. He didn’t need Gen to perform for him. Didn’t want him to.

And for the first time in what felt like eons, Gen didn’t feel like he had to.

Not the way he did for everyone else.

Of course the exaggerated whining still slipped out, the dramatics and the teasing lilt to his voice - but they were more… natural. Not curated and managed for expectations, not tweaked and adjusted to maintain interest, just… him.

His whines would be more nasally, his morning grumpiness not shielded by a smile, his tone sometimes flattening mid-sentence to something closer to his natural cadence without him noticing.

And Senku never so much as batted an eye at it.

Never questioned the inconsistencies or demanded a version of Gen that was easier to deal with. A version of him easier to categorize, to digest. He just… took whatever Gen gave him. Or didn’t give him. 

He didn't do anything about it, didn’t say a word or voice his observations. Didn’t test his new hypothesis, didn’t feel the need to.

There was no point in disrupting something that worked. Something that, for once, didn’t require constant maintenance to keep from collapsing.

But the awareness stayed.

Which might’ve been a bigger issue, because every time he found himself sitting quietly without thinking in Senku’s presence, every time he let a silence stretch unfilled, unperformed…

He knew exactly why.

—

+1 

Gen had always had a type.

And on the surface Senku Ishigami could not have been more opposite.

Except…

Strong, in ways that mattered.

Protective, without hesitation.

Commanding, when it counted.

Thoughtful, observant, kind.

And, perhaps most dangerously, completely uninterested in being anything but wholly and entirely himself.

Begrudgingly, Gen had acknowledged that somewhere along the way Senku had slipped into his range of interest that defied all prior logic and preference. He’d accepted it, managed it, contained it.

Because even if Senku had been interested in romantic pursuits he was far too busy to entertain them. Had too much to do and dreams far too big to be distracted by something as cringy as a crush.

So when Gen leaned into the doorway, intending to deliver a message - something about Chrome needing him, or maybe Kaseki, he couldn’t quite remember anymore - the sight before him was utterly unfair.

Senku had a pencil between his teeth.

Not like a dog with a stick, teeth bared, but with the blunt end held in such a way that it jutted out, bobbing slightly up and down with each twitch of his jaw.

It was a minor thing, almost so inconsequential as to go unnoticed. Except Senku’s brows were furrowed in concentration, eyes sharp as they tracked whatever he was working on, one hand moving quickly across the page in front of him while the other reached up to push the wayward strands of his bangs away from his face.

The motion was impatient, distracted.

Distracting.

Gen’s brain helpfully supplied nothing useful, going completely blank except for a stubborn echo of oh no.

The hand that had been tracing the page dropped to the table, fingers sprawled as Senku leaned a little harder onto it. Gen’s grip tightened on the door frame as a muscles on his forearm bulged just slightly.

Ridiculous.

Objectively, obviously ridiculous.

Gen had seen attractive men before - shared dressing rooms with perfect jaw lines and practiced smirks, flirted lazily over champagne with broad shoulders and effortless charm, kissed his fair share of mouths that could set an audience aflutter with the quirk of a lip.

None of them had ever reduced his thought process to static because they were chewing on a pencil.

Senku shifted, the fabric of his coat pulling across his shoulders as he scrubbed a hand through his hair and made a thoughtful sound, the tip of his tongue tapping the bottom of the pencil in a careful metronome in a rapid flash of pink.

Gen’s stomach gave a dangerous lurch.

Before he could gain his bearings, Senku looked up, brow knit for just a moment. “You feeling okay? You’re all red.”

Managing to make a noise of denial, Gen tried to compose his expression, disappointment flooding him when Senku took the pencil out of his mouth and circled the work bench towards him.

“You better not be getting sick again,” he muttered, pressing a hand to Gen’s forehead before the mentalist could react. 

The touch was brief, clinical, which somehow made it worse. Because while Gen was having a crisis, Senku was completely unaware of the effect he was having on him.

“I’m not sick-ngk-“ Gen’s voice pitched up in surprise when the hand on his forehead slid down to the side of his face.

Cupping his jaw steadily as Senku leaned in to inspect him, muttering to himself about possible symptoms.

Gen stared- at the red eyes inches from his own, the small furrow between his brows, the flash of pink as his tongue darted out to lick his lower lip.

Something inside him snapped.

Before he could stop himself, he leaned forward and closed the small gap between them.

The kiss lasted barely a few seconds before Gen realized what he was doing, jerking back so fast he almost tripped over his own feet.

Senku stared at him, expression one Gen couldn’t quite decipher. He didn’t appear angry or upset, not disgusted, just… surprised?

Gen swallowed before forcing a laugh, waving a hand dismissively, “I must be sick, I think I’ll go lie-“

Whatever response he had expected, it certainly wasn’t Senku kissing him back. One hand had fisted in the front of his haori to stop his retreat, the other settled on his waist with absent confidence, as if it belonged there.

Senku kissed the way he did everything - focused, decisive, and thoroughly. No room for hesitation or uncertainty, just immediate shift from conclusion to action.

Despite himself, Gen couldn’t help but find it incredibly hot.

“About fucking time,” Senku grumbled, pulling back just far enough to take a breath before diving back in. Gen’s knees almost buckled, making a helpless noise when Senku’s tongue pressed against the seam of his lips, high and breathless and needy.

Which Senku immediately took advantage of, hauling Gen closer by the firm grip on his waist. Gen made another embarrassing sound, fingers instinctively bunching in the front of Senku’s coat.

Later, he’d be humiliated at how quickly he lost all higher cognitive function, but in the moment all he could focus on was the way being flush against the lean, solid frame he’d spent months trying very hard not to fantasize about felt.

By the time Senku pulled back, Gen was practically panting for air, blinking at Senku with unfocused eyes. Senku wasn’t much better, hair even more of a disaster than usual from Gen’s fingers carding through it, pupils blown wide and lips kiss swollen, curled into a smug, self-satisfied smirk.

“Glad to know that’s what your problem’s been the last few months.”

Gen took a few beats to reply. “My…? Huh?”

“You’ve been acting weird for a while. Had a few ideas of what might’ve been going on, but eventually narrowed it down.”

“...A few ideas?”

Senku shrugged, hand still distractingly warm against his side. “Parasite, vitamin deficiency, finally cracking under the stress and having some sort of prolonged psychological episode. Figured if you actually did like me and wanted something to happen you’d say something, so when you didn’t I had to get creative.”

“Your first thought was I had a parasite?”

“Third, technically,” Senku replied. “I figured you liked me but you kept acting like you did and didn’t at the same time and I wasn’t going to be the first idiot to make a move if I was reading it wrong… But in hindsight, you blushing every time I touched you should’ve been a dead giveaway.”

Gen opened and closed his mouth once, heat creeping up the back of his neck, annoyingly proving Senku right. Something the scientist clearly noticed if the way his smirk sharpened in vindicated amusement had anything to say about it.

“You are insufferably proud of yourself for someone who thought I might have worms before thinking I might have a crush on you…” Gen grumbled, eyes askance. 

“Eh, still not ruling it out.”

Gen couldn’t decide whether he wanted to kiss him again or shove him - both impulses had their merits.

Instead, he laughed. “You are unbelievable,” he managed, voice soft in a way that didn’t quite match the heat he felt in his cheeks and his chest.

Senku snorted, making the decision for him and pressing a quick kiss to his lips before finally pulling back. “Says the guy who spent the last few months looking like he either wanted to fight me or climb me.”

“I’m going to throw myself in the river,” Gen groaned, hiding his face in his hands. “Why didn’t you say something when you noticed?”

“Like what?” Gen peered through his fingers to see Senku leaning back against the workbench, completely relaxed as if he hadn’t just upended Gen’s total understanding of the last several months. “You keep looking at my hands like you want them in your mouth, what’s up with that??”

Gen made a strangled noise in a pitch he wasn’t aware he could reach. Senku blinked at him once, not even trying to hide the smug amusement of his expression.

“Stop looking at me like that,” Gen grumbled weakly, palms pressed to his cheeks in a vain effort to leech some of the heat away.

“Like what?”

“Like you know things.”

Senku raised a brow, “I do know things. Sort of my whole thing.”

Gen groaned, “That attitude is exactly why no one should ind-fay you attractive!”

“Didn’t stop you.”

Gen would’ve been annoyed by how unrepentantly smug Senku sounded, but he was distracted by the way the other man looped two fingers under the string of his obi and tugged him close again. It wasn’t a rough jerk, more of a firm suggestion, and Gen’s feet moved him forward before he had time to even think about it, settling between Senku’s thighs as warm hands found his waist again.

And, because the universe apparently hated him that day, Senku looked unbearably pleased.

“Huh, you really do like getting manhandled, don’t you?”

“Nope, conversation over,” Gen pushed at Senku’s chest, absolutely not reacting at how the grip on him tightened or how firm his chest felt under his palms. “I’m going into the woods to let nature reclaim me.”

Senku laughed, letting him struggle for a moment without letting go. “No can do,” he said easily, thumbs absently rubbing against Gen’s sides through the fabric of his yukata. “I need you alive - we’re short staffed.”

Gen tried very hard not to melt into some sort of shameless puddle, which was particularly difficult by just how comfortable Senku seemed to be with holding him. He’d spent months internally imploding over every accidental touch and gesture, every smile and absentminded bit of kindness, convinced that it would never lead to anything - only for Senku to do what he always did and completely upend all expectations.

And, as always, Gen knew there was nothing to do but go along with it.

“You’re lucky you’re cute,” he grumbled, dropping his forehead to Senku’s shoulder, biting back a pout at the resulting laugh.

“Cute, huh? Didn’t realize that was your type.” 

Gen was about to give a snarky reply when Senku adjusted his grip - the move almost instinctual, as if he’d already gotten used to holding him - realizing just how natural it felt.

Which was really the most unfair thing about it all. Not the teasing or the unexpected reciprocation of his feelings, or even the fact that Senku somehow managed to fit every trait Gen liked despite seemingly completely wrong on paper.

Just how safe it felt.

How easy it was to fold into Senku without thinking. Warm and solid against him, accepting everything Gen gave him with the same straightforward certainty he approached everything else with. 

Shifting just enough to look up, Gen felt butterflies race to his stomach at the unbearably soft look Senku was directing at him, giving in to the urge that had plagued him for longer than he could truly remember. 

“Neither,” he murmured, lips brushing against Senku’s as the other man leaned in to meet him, “did I.”