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The thing about geniuses - true, unhinged, civilization-rebuilding, walking-inventor geniuses - is that no one really expects them to crack.
Not physically. Not emotionally. Not in any visible, fallible, human way.
So when Senku started taking slightly longer than usual at the lake one evening after their hard-earned victory on Treasure Island, no one thought twice.
Taiju and Yuzuriha had noticed, sure. But it was Senku. The man regularly scrubbed his hands raw with soap and made everyone gargle saltwater like it was a religious rite. The guy had literally invented shampoo halfway through a guerrilla science campaign just so he wouldn’t feel gross after going twelve rounds in the mud with the world’s nastiest megalomaniac. If anyone was allowed a little extra rinse time, it was him.
Besides, no one had medicine. No clinic. No ER. Staying clean was their first, last, and only line of defense. So Senku taking his sweet time scrubbing off every trace of Ibara-cooties? Seemed par for the course.
Until Suika came running.
"Chrome! Gen!" she gasped, eyes wide behind the melon helmet. "Do you know what's wrong with Senku?!"
"Uh… washing up outside?" Chromne blinked. "Why? You need him?"
Suika nodded, breathless. "Suika wanted to ask about the lab car but—he's weird. He looks weird. Like, Ruri-level sick weird. I think—I think something’s wrong!"
There are a few phrases that hit the Kingdom of Science like a punch to the collective gut. “We've run out of sulfuric acid.” “Ginro wandered into the poison swamp again.” “Someone wants to be the new Tsukasa/ Hyoga” but “Senku looks sick” might’ve topped them all.
By the time Gen and Chrome caught up, Suika was already half-sprinting, half-stumbling back toward the trees.
“He—he looks different! Like, not-Senku different!”
Gen and Chrome exchanged a look.
“…She’s not exaggerating, is she?” Chrome asked, half-joking.
Gen shook his head, already moving. “Nope. And if this turns out to be our beloved science gremlin doing crazy experiments right after our crazy adventure, I’m out.”
They found him under the trees, a little ways from the lake.
And for a second, both of them froze.
Because Suika had not been exaggerating in the slightest.
Senku was leaning against a tree, half-dressed, shirt tugged over his shoulders but left hanging open, bandages loose. His breathing was a little too fast, the flush on his pale face a little too intense. His usual spiky mop of hair—gravity-defying, stress-fueled, and recognizable from literal kilometers away—was down. Completely. And it flowed. Soft, fluffy, glinting faintly in the dappled forest light like some cursed shampoo commercial. Somehow both ridiculous and... borderline ethereal.
And with the greenish tinge in his pale hair, the fever bloom on his cheeks, and his lean figure silhouetted by the forest behind him –
Yeah. He looked less like a mad scientist and more like an overworked forest spirit slowly phasing out of existence.
“Take a picture,” Senku rasped, breath hitching, “it’ll last longer. But wait—all the cameras are back home. So you technically can’t.”
“Oh thank god, no one can document this,” Gen muttered, equal parts relieved and horrified. “Senku-chan, I say this with love: you look like a fever dream cosplay of yourself.”
“That’s ‘cause I’m halfway to actual fever dream,” Senku admitted with a breathless chuckle. “Kukuku… turns out… body’s dealing with the whole ‘open wound’ thing. Should’ve, ah… rested before skinny-dipping like an idiot. But hey. Less gross equals less chance of infection.”
“You’re burning up!” Chrome snapped out of his stunned stupor, rushing to Senku’s side. “You should’ve told someone! You could’ve - ”
“Died? Yeah, I know,” Senku said, a little too casually. “Can’t do that yet, gotta meet Whyman before he wiped us all out for real.”
Gen winced.
That was the thing with Senku. He always had the worst thoughts tucked away somewhere in his head like rejected equations - filed, minimized, but never deleted.
“I was just… buying time until we’re more or less good to go. Thought maybe if I cleaned up enough, stayed upright long enough, I could ignore it. Hit the off switch on all the pointless alarm bells.”
Gen squatted beside him, inspecting the wound—red, inflamed, definitely angry.
“And how’s that working out for you, hmm?” he asked lightly.
Senku gave a weak smirk. “Turns out… not great.”
“Right. We need Taiju,” Chrome said, already standing. “He can carry—”
“No,” Senku groaned, dragging a hand across his forehead. “The big oaf would shout very loudly. My head’s already got its own percussion section. He’d also broadcast this embarrassing affair to the whole island. Somebody get Kohaku and Kinro instead. They’re reliable. Steady hands. Not so much fanfare.”
Gen blinked, then smirked. “So you’re assigning your own rescue squad now?”
“Don’t want to die and be humiliated,” Senku muttered.
“I’ll get them!” Suika squeaked. “Suika will help Senku feel better!”
“Wait,” Chrome said quickly. “Senku—what do we need? For your fever, for the wound—tell us everything.”
Senku closed his eyes, breath shallow, but his brain hadn’t shut off yet. Not even close.
“…Cool the fever first. Use cloths soaked in stream water. Replace often. Hydration’s priority two. Water, ideally boiled, cooled, mixed with salt and sugar—makeshift oral rehydration solution. One liter water, six teaspoons sugar, half teaspoon salt. Stir well. Third—clean the wound again. Soap and water. If we’ve got ethanol or Kohaku’s tinctures, use them. Re-bandage with something sterile. As sterile as possible.”
He paused, blinking blearily. “After that, pray. We don’t have antibiotics.”
“You made antibiotics once,” Gen said gently.
Senku gave a tired smile. “Yeah. Took months. Can’t do a penicillin speedrun in a fever haze.”
“Right,” Chrome said, turning to Gen. “So. Boil water, gather clean cloth, re-wrap the wound, make Senku drink weird sugar-salt tea, keep him from dying. That about it?”
“Add ‘stop Suika from crying’ and we’ve got ourselves a plan,” Gen said, already standing. “I’ll get Yuzuriha too. If anyone can whip up soft bandages, it’s her.”
Senku let his head fall back against the tree, eyes half-lidded.
“…Ten billion percent inconvenient,” he murmured. “Should’ve let someone else win the battle royale against Ibara.”
Gen looked at him, fond and exasperated. “Yeah, but then we wouldn’t get to see this once-in-a-lifetime forest nymph cosplay. Silver linings, Senku-chan.”
Senku huffed a weak laugh. “Just don’t let Ryusui see. He’d never shut up about it.”
“Oh don’t worry,” Gen said darkly. “If I have to, I’ll gaslight and memory-wipe the entire island. No one sees you like this but us.”
Coming from Asagiri Gen, Senku one billion percent believed him.