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If Senku was in a better frame of mind he would have been annoyed at himself for not noticing sooner.
The fatigue, the muscle aches, the rasp of his throat - he’d waved each symptom away without a second thought.
He’d pulled an all nighter, of course he was tired.
His muscles ached from carrying heavy baskets around the village clearing.
His throat was dry because he’d forgotten to hydrate.
All easily explained, even as he struggled to open his eyes against the mid-morning sun blinding him through the window.
“It’s not like you to eep-slay in, Senku-chan,” Gen teased, giving him a gentle shake. “We really need to work on that sleep schedule of yours.”
Senku pushed himself to sit, wincing against the throbbing of his head and the pressure in his sinuses. “Yeah, ye-“
His grumble dissolved into a coughing fit that he tried to stifle into his elbow, shoulders shaking with the force of it. The room tilted unpleasantly as his vision began to swim at the edges.
Gen’s smile fell, hands quickly reaching out to steady Senku as his coughing fit continued. “Whoa there, easy… easy.”
“I’m-“ Senku sucked in a sharp breath that scraped down his throat like sand paper, “-fine.”
“You are very clearly not fine.”
“It’s just a cold… knock it off.” Gen had pressed the back of his hand to his forehead and Senku tried to wave him away, arm weak and limp. “My immune system is handling it.”
“Which is why you’re burning up and barely able to sit up,” Gen chided, shaking his head at how warm the other man’s skin was.
He gave another lackluster push to try and put some distance between them. “I said I’m fi-“
The floor rushed up faster than Senku expected and if not for Gen’s firm grip on his shoulders he would have found himself slumped in an inelegant heap on the floor instead of against the mentalist’s side.
“Fine, huh?”
Gen shifted his grip, adjusting Senku until he was tucked back into his bedroll, ignoring his protests and grumbles. “I’ve got work to do…”
“Not today you don’t,” Gen huffed, tucking the blanket more securely around him even as Senku tried to wriggle free. Any other day his lackluster attempt would have been comical, but as Senku opened his mouth to argue only for another coughing fit to tear through him it was anything but.
With his arms pinned to his sides, all he could do was turn his head away from Gen, trying to keep his mouth closed the best he could.
It left him breathless, chest aching and throat burning. Once it subsided, he realized Gen was gently rubbing his chest in small, soothing circles, looking at him with obvious concern.
“I can take care of myself,” he rasped.
It came out reflexive, automatic almost.
Gen paused, something flickering in his eyes for the briefest of moments. Understanding, almost.
Senku had gotten used to patching his own scrapes, watching his own fevers, dragging himself through illness so as to not make Byakuya worry. Senku had always been somewhat independent and that trait only solidified further once Byakuya joined NASA - he knew that at the first sign of trouble his father would be on a flight back to Japan regardless of any other responsibilities.
Waking up alone in a stone world had outright cemented the habit.
“I’m sure you can,” Gen murmured softly, head tilted and hand still a gentle weight on his chest. “You’re Senku-chan, after all, you can do anything.”
Senku was about to argue against the obvious sarcasm.
“But even chiefs are allowed to take a sick day.”
He snorted weakly despite himself, regretting it immediately when he dissolved into another coughing fit. Gen winced in sympathy.
“It’s not a sick day,” he muttered hoarsely when the coughs subsided, “it’s a minor viral infection. It’ll resolve itself in a few days.”
“Yes, if you rest.” Gen chided, palm resting flat on Senku’s chest. “Something you’re not very good at.”
“You just said I’m good at everything.”
Gen raised a skeptical brow - at both the words themselves and the petulant tone they were said in. “No, I said you could do anything. Doesn’t mean you’re doing it well.”
His thumb was making slow, absent minded circles against Senku’s sternum and he found himself thinking that he'd never really noticed just how big Gen's hands were. Senku could feel his eyes growing heavy, hating to admit that the gesture did actually feel somewhat nice.
“How about this, I’ll go get you some tea to soothe your throat and after that you can go about your business.”
Something about Gen’s tone was suspicious, but with his strength sapping away Senku struggled to place why. His limbs felt like lead, body sinking deeper into the bedroll, the gentle rub of Gen’s thumb maddeningly distracting.
“It’ll make me feel better,” the mentalist wheedled, and Senku finally conceded.
“...Fine,” he muttered, the room softening at the edges and eyes drifting shut. “But no drugging me.”
Gen laughed and Senku felt it rattle through his chest, “Hmm, you caught me. And here I was hoping for the chance to play mad scientist while you were out of commission.”
“I’m not out of commission,” Senku grumbled, voice weak and slurring as sleep dragged at him harder than he wanted to admit. “Just taking a little… break…”
He barely registered Gen’s hand leaving his chest, the cool air that followed, or the quiet shuffle of footsteps retreating from his side.
–
He drifted.
His body felt too heavy, like stone before revival. His thoughts fell through his fingers like water, scattering and reforming into strange, disconnected loops.
There was a hand in his hair. Fingers carding gently through sweaty strands, smoothing them back from his forehead in a way that was far too familiar.
“Always overdoing it, aren’t you?”
The voice wasn’t Gen’s. Warmer, rougher, fond in a way that ached.
Senku blinked his eyes open, finding himself much smaller than he should’ve been. Younger, laid in a familiar bed beneath a patched, plaster ceiling festooned with stick on glow-stars and surrounded by the soothing scent of well-known detergent and aftershave.
“Dad?” he croaked, wincing at the way it crackled up his throat.
Forcing his vision to focus, he found Byakuya smiling down at him, eyes crinkled at the corner. There was a damp cloth in his hand and he pressed it to Senku’s forehead with exaggerated care.
“Gave me quite the scare there, kiddo,” he murmured.
“I’m fine,” Senku insisted automatically, which was ridiculous because he could hear just how congested he sounded, even with how high and small his voice had become. “It’s just a cold.”
“Mm-hmm,” Byakuya sat on the edge of the bed, careful not to jostle him. “Even colds need rest to get better.”
“Tch,” Senku scoffed, “you sound just like the Mentalist.”
“Do I, now?”
The cool cloth dragged gently over his temple, over the bridge of his nose, chasing away the worst of the heat and the sticky sweaty feeling. “Yeah… annoying.”
Byakuya laughed, bright and unabashed. “Annoying, huh? He must be important.”
“That’s not how that works,” Senku grumbled, cracking an eye open.
“Sure it is,” Byakuya’s grin softened, hand smoothing the hair back from his forehead and resting warm and solid on the top of his head. “You only let important people boss you around.”
“I don’t let anyone boss me around,” he gruffed, trying to push onto his elbows. His vision swam, the pressure behind his eyes intensifying, and he fell back with a cough and a pained groan.
The hand in his hair began to move, combing through in slow, steady strokes. Not hurried or distracted, just there.
Grounding. Reassuring. Soothing.
“You know,” he said quietly, “you don’t have to do everything alone.”
The room flickered. Plaster fractured into roughly hewn wood, crisp chemical cotton scent replaced with smoke and damp earth.
But the hand in his hair didn’t change.
“You looked so small back then,” Byakuya continued, voice sounding strangely distant. “Even when you were acting so big.”
“I wasn’t small,” Senku protested, eyes slitting open to look up at the familiar face. Byakuya was suddenly older, closer to how Senku remembered him on their last video call before… well, before.
Goatee beginning to speckle with the odd gray hair, crows feet forming at the corners of his eyes.
But that same familiar smile. The same proud expression.
“You were,” he said gently.
His fingers traced lightly along Senku’s hairline before sweeping back again, far more reassuring than they had any right to be.
“And you still are sometimes.”
The words twisted in Senku’s chest. He missed it.
Missed the uncomplicated certainty that someone was there. Hovering, worrying, caring without being asked.
Missed the quiet, reassuring weight of a hand in his hair.
Missed his dad.
The ache opened up inside him, raw and unscientific.
“But,” the voice continued, further away but bright with the tone Byakuya always used when he knew something Senku didn’t, “you’re not alone.”
The hand kept moving, slow and steady. Grounding.
“You’ve got people now.”
The room flickered again, the smell of herbs sharpening in the air, the faint sound of music filtering through the haze.
The warmth beneath Senku’s head felt… different.
Byakuya’s voice faded out like a radio drifting out of range.
“Try letting them take care of you sometimes, Senku.”
The song changed.
It wasn’t one of Byakuya’s off-key ballads where half the words were nonsense anymore.
It was quieter. Smoother. Playful, even in its softness.
Senku’s brow furrowed, suddenly aware that the downy pillow beneath his head had been replaced with something warmer and firmer.
Fingers still moved through his hair in slow, careful strokes. From temple to crown, crown to nape, pushing it back from his damp forehead and tracing along his scalp in the exact same rhythm as before.
Someone was humming. Softly, almost shyly.
Senku’s eyes cracked open.
The ceiling was familiar wood, the air smelled like smoke and herbs even through the stuffiness of his nose, along with a surprisingly comforting scent of flowers. Above him, looking down with an expression so unguarded it almost didn’t fit his face, was Gen.
The humming faltered when he noticed Senku’s eyes were open.
“Oh… are you actually awake this time?”
Senku stared at him as Gen adjusted slightly underneath him, repositioning Senku’s head more comfortably in his lap. His hand stilled for only a moment before resuming its slow path through Senku’s hair.
“You were in and out for a while,” he continued, voice a low murmur. It made something in Senku’s chest tighten and loosen in different ways. “You talked in your sleep a few times… I think at one point you threatened to fist fight a microbe.”
“I’d win,” Senku rasped, struggling to keep his eyes open.
Gen smiled, small and fond, eyes crinkling up at the corner as he exhaled softly through his nose. “I’m sure you would. Senku-chan can do anything, after all.”
Silence settled between them, gentle and unhurried.
Senku used what little strength he had to catalogue a few things.
His fever had broken, or at least dipped, the pounding in his skull dulled and fatigue weighing him heavily.
He had been drooling, a wet splotch on Gen’s haori cold against the shell of his ear.
Gen hadn’t moved after realizing he was awake. Hadn’t made a move to shift Senku back to his pillow, hadn't stop the steady comb of fingers through his hair.
Instead, his free hand had come up to rest lightly against Senku’s shoulder as if to hold him in place. This thumb moved in small circles, absently but reassuring. Nails scratched lightly against the skin of his scalp in a way that sent a warm, molten feeling down his spine.
He realized after a moment that he’d lost track of time, breath catching slightly in his chest. Someone, most likely Gen, had closed the window and it was difficult to parse the time of day based on the dimness of the observatory.
He was about to sit up when the hand on his shoulder increased its pressure just a hair. “It’s just about evening,” Gen said softly, “you slept most of the day away.”
Senku felt himself relax, absently wondering how Gen had known exactly what he needed to hear before waving the thought away. Gen always somehow knew exactly what Senku without ever asking, oftentimes before Senku even knew himself.
“That sucks,” he found himself murmuring, “there was a lot to do today…”
The fingers in his hair slowed, tracing the curve behind Senku’s ear before sweeping back through his hair again. The repetition made it difficult to keep his thoughts aligned. Every time Senku tried to focus on something - inventory management, calculating his recovery time, plans to make acetaminophen - they scattered under the steady rhythm of Gen’s gentle touch.
It was… unfairly effective.
“I hate feeling useless,” he finally mumbled, the words rough and stripped of their usual sharp edges.
Gen didn’t react with surprise or tease him, just continued to comb through his hair with his fingers, “You’re not.”
“I can’t even sit up.”
His hand didn’t falter. “So don’t.”
Senku frowned, “That’s not how-”
A cough interrupted him, weaker than before, more irritated than violent. Gen waited it out, thumb resuming its slow path along Senku’s scalp once the worst of it passed.
“Ugh, I’m going to end up getting you sick, too.”
Gen’s lips curved faintly, eyebrow raised in amusement. “I’ve already accepted my tragic fate. If I perish in the line of nurse duty, please carve something flattering on my gravestone.”
Senku found himself grinning despite his best efforts, “Here’s lies Gen, Died because he has zero survival instincts.”
“Mm, two out of ten, you didn’t even think to mention my beauty or charm.”
The teasing was gentle, automatic, but Gen’s hand never stopped moving. Fingers slid through Senku’s hair with absent precision, careful not to tug or press too hard. His other hand remained a steady weight on Senku’s shoulder, thumb drawing absent circles every so often through the fabric of his tunic.
Senku gave a huff of a laugh, vaguely noting that he didn't feel nearly as restless as he would usually be in his current situation. Any other time he would be chomping at the bit to get back to work regardless of what his body seemed to think necessary. Fighting tooth and nail to get out of bed and do something productive, no matter how small.
Instead, tucked against Gen’s lap, exhaustion dragging him under in slow, heavy waves, he didn’t feel restless at all.
He felt… safe.
“Besides, even if I do catch it,” Gen continued expression softening and something unbearably fond flickering across his face, heedless to Senku's realization, “I’ll simply be as dramatic as possible about it. You’ll feel obligated to take care of me, be at my every beck and call. It will be a marvelous bonding experience for us.”
Senku snorted, the sound dissolving into a congested huff. “In your dreams, Mentalist.”
“You can be surprisingly attentive when you want to be, Senku-chan. I think you’d make a wonderful caretaker while I was convalescing.”
“Tch, I’d just drug you into a coma and call it a day.”
“Oh, so uel-cray,” Gen’s fingers drifted down to trace lightly at the nape of Senku’s neck before sweeping back up, slow and deliberate. “Is this how you treat your handsome nurse? Most people would be thrilled to be in your shoes right now, you know.”
Senku tried to roll his eyes or muster up a glare, but it lacked any real bite. His eyelids felt heavy again, thoughts dragging like they were wading through syrup. He could still feel the ghost of his fever dream - his father’s voice, the steady warmth of a hand stroking his hair.
The sensation hadn’t changed, just the person.
“You were humming,” he muttered, words slurring at the edges as he struggled to keep his eyes open. “It was nice.”
The fingers in his hair stilled for just a heartbeat before resuming their slow, steady rhythm. “Thought it might help,” he said quietly, so low that it was almost swallowed up by the room’s soft shadows. “I’ve never seen you sleep so deep, not even after several all nighters.”
Senku could feel more than hear the slight hitch to Gen’s voice, how his weight shifted underneath him.
“I was worried.”
The admission made Senku’s chest tighten. He wanted to tell Gen it was unnecessary - a cold was nothing compared to Ruri’s pneumonia or the plethora of other ailments that were of far more concern without the aid of modern medicine - but the words faltered before they could form.
His throat still burned, his muscles still ached, and every move felt like his limbs were laden with heavy stones.
Senku realized he had been silent for too long when Gen’s hand started to lift away and he managed to shift just enough to nudge his head against the retreating fingers.
“You’re good at this,” he rasped, voice hoarse and hesitant, almost shy. "I usually fight it.”
He didn't clarify what, didn't need to.
A breath passed between them. And then a second.
And then the gentle stroke of Gen’s hands through his hair continued.
“I know,” Gen said simply, but there was no teasing to it. Only softness and a deep well of patience Senku realized he often took for granted. “And you’ll still fight me next time, too, I’m sure,”
Senku didn’t bother arguing, eyes drooping and resistance dissolving under the soothing weight of Gen’s hand and the warm press of his body against him. Muscles unclenched and the lingering tension of days, weeks, months of pushing himself evaporating into the quiet stillness.
He shifted again, enough to rest his cheek more comfortable against Gen’s lap, nose brushing against the fabric of his haori. It smelled faintly of the air around the forge, slightly salty from the sea air, the flowers he always seemed to carry - a scent he hadn’t realized had become such a comforting constant.
It took him a moment to realize that Gen had started humming again, soft and entirely deliberate, Senku’s mind starting to drift. Not towards plans or calculations or inventions, but to the last clear image from his fever dream.
You’re not alone.
He hadn’t realized just how tightly he’d been clinging to that old instinct, the notion that he had to take care of himself, until someone simply… refused to let him.
“You know,” he murmured, voice hoarse and hesitant and slurring a bit as he slowly lost the fight against sleep, “I don’t usually… let anyone…”
Gen didn’t press or tease even as he trailed off into a somewhat frustrated grunt, sounding more like a grumpy toddler than anything. He just adjusted Senku’s head slightly, alleviating the slight strain he hadn’t even noticed was starting to prickle at his neck, touch ever so gentle but all too reassuring.
“I know.”
Senku leaned into the brush of fingers against his temple, completely disarmed by the soft warmth of care and the steadiness of Gen’s presence. He found himself completely unable to cling to his usual pride and independence, and for the first time in a long while reluctant to even try.
“You’re gonna make me… get used to this…”
Gen’s hands stilled for a moment.
The one resting on Senku’s shoulder curled faintly in the fabric of his coat, fingers tightening as if on instinct before relaxing again. For just a breath, Senku thought Gen might pull away - laugh it off and put some distance between them as they both were wont to do when attention was drawn to just how often they tap-danced around the blurring line between friendship and something more.
But he didn’t.
Instead, the thumb on his clavicle resumed its slow, absent circles, somehow even gentler than before.
“You really don’t make this easy, you know,” Gen murmured softly, and even with his eyes closed Senku could picture the small smile on his face and knew the mentalist wasn’t referring to being a good patient.
Grunting weakly in acknowledgement, the sound barely there, Senku shifted, chasing the warmth of Gen’s lap as his breathing continued to slow and even out. Senku felt more than heard the way Gen’s breath hitched, nudging his head into the way Gen’s thumb brushed lightly behind his ear.
The humming resumed, softer than before, a melody Senku still didn’t recognize. Something gentle and wandering, Senku paying more attention to the way it rumbled in Gen’s abdomen more than the sound itself as sleep tugged at him more and more.
Just as sleep finally pulled him under, Senku felt his own fingers curl loosely into the edge of Gen’s sleeve, loose but persistent. Not a grip meant to hold him in place or as a demand.
Just… contact.
Maybe his dad had been right after all.
Sometimes it was okay to be small for a little while, so long as someone was there to take care of you.