Archive of Our Own ^beta

Chapter Text

Senku Ishigami had long accepted that most people were... idiots.

It was a fundamental truth of the universe, just like gravity or the fact that chemical reactions would always follow the laws of thermodynamics. However, he had not expected the universe to personally screw him over like this.

There was a single slip of paper pinned to the school bulletin board. A notice. A death sentence.

DUE TO UNFORESEEN CIRCUMSTANCES, THE SCIENCE CLUB WILL BE SHARING ROOM 3-B WITH THE ATHLETIC CLUB UNTIL FURTHER NOTICE.

THANK YOU FOR YOUR UNDERSTANDING.

– The Student Council

Senku stared at it.

Chrome, standing beside him, choked on his drink.

Gen, who has followed them just to witness the carnage, whistled.

“Ah, Senku-chan,” Gen said with fake sympathy, “looks like your personal kingdome just got annexed. By barbarians.”

“Over my dead body.” Senku muttered. He yanked the notice off the board, crumpling it into a ball.

Chrome, still processing, looked horrified. “Wait, wait, hold on—does that mean all our stuff is gonna be in there with them?! Like—our experiments?!” He tossed his drink aside as he fell into step with Senku and Gen. 

“Yes,” Senku said darkly, rubbing his temple.

“The chemicals?”

“Yes.”

“The machines?”

“Yes.”

“...the dangerous, highly explosive equipments?”

“Chrome, when are they not dangerous and highly explosive?”

Gen grinned. “On the bright side, we might get some interesting results if an experiment accidentally explodes on the treadmill.”

Senku dragged a hand over his face. He could already see the disaster unfolding in his mind. The Science Club had always functioned in controlled chaos—it was an ecosystem of wires, bubbling solutions and possibly illegal engineering projects. Meanwhile, the Athletic Club was a mass of sweat, testosterone and the faint smell of overpriced protein powder. And while he did understand the importance of athleticism, in this case, it only proved to be an obstacle to him.

He feet dragged over to that damned club room—his club room.

The one he's been using since he started high school and formed a formidable Science Club with the others. 

With determined steps, he threw open the door...

...gone.

The first thing Senku notices is that his lab tables were gone.

The second thing he noticed was that in their place were three squat racks, a row of free weights, and the presence of multiple very large, very muscular people.

The third thing he noticed was Tsukasa Shishio, standing in the middle of the chaos like some mythical warlord surveying his domain.

Senku narrowed his eyes.

Tsukasa was the captain of the Athletic Club, the school’s top athlete, called the strongest high school primate, and the unfortunate owner of hair that looked like it belonged in a shampoo commercial. How... how was that even possible? He also had—Senku notes—the correct amount of mass, muscle and from what he's heard, strength for Senku’s not-so-legal experiments, thought that's not why he's here at all.

Senku had more than enough opinions on Tsukasa.

Mostly that Tsukasa was absurdly overpowered at everything—track, martial arts, judo, weightlifting, even the occasional casual basketball game. It was statistically unreasonable for one person to be that physically competent. It'd be a lie, ten billion percent, if he said he didn't think that was amazing at all.

But this was the man who he was sharing a club room with—

Tsukasa turned as they entered, looking calm and slightly amused. “Ah, you must be the Science Club.”

Senku crossed his arms. “You must be the invasion force.”

Chrome made a distressed noise behind him.

Tsukasa’s lips twitched like he was fighting back a laugh. “It wasn't my decision. The Student Council said that the Athletic Club could share the space.”

Senku glanced at the sheer amount of weights, training mats, and gym equipment now crammed into what had once been his workspace. ‘Share’ was an extremely generous term.

“I see,” Senku said, deadpan. “So where’s our share of the space?”

Tsukasa pointed to a corner.

Senku followed his gaze.

There, shoved into a small corner by the window, was a single desk, a chair, and a shelf with a few scattered beakers.

A single desk.

For the entire club.

Gen made a choked sound that might have been laughter.

Chrome looked ready to pass out. “That’s it?! That’s all they gave us?!”

Senku slowly turned back to Tsukasa. “You expect me to compress my entire scientific genius into that shoebox-sized workspace?”

Tsukasa shrugged. “You work with chemistry, right? I thought you’d enjoy the challenge.”

There was a brief, tense silence.

Gen beamed. “Oh, this is gonna be fun.”

Senku exhaled slowly. Then, with complete neutrality, he walked over to the single desk, dragged it into the middle of the room, and slammed it down like it was a declaration of war. 

“Fine,” he said. “I’ll work here. But if anything from the Athletic Club damages my equipment, I’m billing you.”

Tsukasa smiled in a way that was far too calm. “Likewise. If your experiments interfere with training, I’ll expect you to clean up the mess.”

They stared each other down.

There was an invisible energy shift.

Chrome, sweating: “Uh. Guys?”

Gen, practically vibrating with excitement: “No no, let them cook.”

The standoff stretched for several beats—an unstoppable force and an immovable object locked in their first official battle.

Then, finally, Tsukasa gave a small nod.

“Alright,” he said. “Let’s share the space, Senku.”

He walked away.

Senku hated that he used his first name.

“You guys still don't have much space though,” A voice pipes in. Collectively, they turn to see Kohaku standing there, a hand resting on her hip, adorning stereotypical gym clothes. “I doubt you'd be able to—I don't know—blow something up with that amount of space.”

To that, a cackle—yes, a fucking cackle—escaped Senku’s lips, which had curled into a nasty grin which usually didn't mean good. “Oh, I have plan for that.”

“I’m kinda... scared.” Chrome whispers, near Gen’s ear.

Gen giggles in response. “And I'm going to be rich, Chrome-chan.”

-

Senku Ishigami did not wake up early. Ever.

Mornings were a waste of time when the true magic of scientific discovery happened at three in morning, under the glow of his laptop screen and the comforting crackle of something definitely not flammable bubbling away in a flask. Oh, and Taiju’s snores from the other bedroom.

But today was an exception.

Today, Senku dragged himself out of bed at 4:30 AM, fueled by the purest form of motivation known to mankind: Petty Spite.

Tsukasa Shishio, in pure dictatorship form had stolen—yes, stolen—a shared space and Senku wasn't going to take that sitting. He wouldn't let that slide. 

Thus, at 5:00 AM sharp, armed with beakers, glassware and enough lab equipment to make the school board nervous, and a sleepy Taiju carrying the other half of the equipment, he stormed the school. His grand plan had three simple phases:

Phase One: Arrive first. (Check.)

Phase Two: Expand Science Club’s borders. (Check.)

Phase Three: Make it as difficult as possible for Tsukasa to function. (Pending execution.)

Senku set up everything. Tables, shelves, even the damn bench press had become a surface for his chemical solutions. A distillation rig sat where the dumbbells used to be, happily bubbling with something that probably wouldn’t explode.

“Senku,” A yawn left Taiju’s mouth. “Won’t Tsukasa get angry? And besides, I'm also on the athletic club!”

“This is just payback, you big oaf, and I doubt that muscle head is going to kick you out of the club for such a dumb reason.” Senku huffs, carefully placing another flask. While this was payback, most of the things he had placed were of exponential value, so treating them with care was a must.

He sighed and walked towards his desk, sighing as he leaned back on the chair he had snagged from the teacher's lounge.

Now, he just had to wait.

By 6:30 AM, the air reeked of sulfur and vaguely concerning chemicals.

By 7:00 AM, Tsukasa arrived.

The moment he stepped into the room, he stopped short. His athletic club’s half of the room had been completely invaded.

“Really?” Tsukasa asked, his voice calm but edged with irritation. “I thought we discussed this yesterday, Senku. The Athletic Club needs this space.”

Senku, hunched over his workstation, didn't even look up from the beaker he was carefully measuring. “Correction, Tsukasa. You moved my stuff without preamble and assumed the entire space was yours. I ignored it because, as I said before, there’s no way in hell I’m moving my lab just because you and your judo gang decided you need a bigger space to throw each other around.”

Tsukasa exhaled sharply. “Senku, try to be reasonable. The Athletic Club’s current room is too small. We’ve got new members, and it’s becoming dangerous to practice in such a tight space. Someone’s going to get hurt.”

Senku finally looked up, eyes gleaming with that insufferable smirk. “You know what’s actually dangerous? Me trying to run a controlled chemical reaction in some dusty storage closet just because you can’t figure out how to rearrange your mats properly.”

Across the room, Chrome—who had arrived a few seconds after Tsukasa, caught in the middle of it all—let out a weak laugh, trying (and failing) to diffuse the tension. “H-Hey, guys. Maybe there’s a way we can—”

“No.” Both Tsukasa and Senku cut him off simultaneously, their glares so sharp that Chrome instinctively took a step back.

“Science has been here first, Tsukasa. You can’t just storm in and claim territory like some ancient warlord,” Senku continued, tapping his temple. “This isn’t the Stone Age.”

Tsukasa’s lips twitched, barely holding back a smirk. “Ironic, considering you always act like a caveman when someone disagrees with you.”

Gen, who had been leisurely sipping his drink at the back of the room, sitting beside Taiju, perked up at that. “Oho, now that’s a good one.”

Senku rolled his eyes. “If anyone here’s acting primitive, it’s you. Resorting to brute force to get what you want instead of engaging in intellectual debate—”

“Intellectual debate?” Tsukasa scoffed. “Senku, your idea of debate is throwing around complex words until your opponent either gives up or leaves the room.”

"And your idea of debate is just standing there looking intimidating until people cave!"

Outside the lab, Kohaku and Ryusui had stopped in the hallway, listening in with varying degrees of amusement. The other members of both the clubs had gathered as well—equally entertained with the argument that was happening inside.

“How long have they been at it?” Ryusui asked, adjusting his cuffs with a smirk.

Kohaku sighed. “Since morning. At this rate, they might actually end up killing each other.”

Back inside, the argument had evolved (or devolved) into a rapid-fire exchange of insults that, somehow, still sounded vaguely intellectual.

“You’re stubborn beyond logic,” Tsukasa shot.

“You’re emotionally attached to your club like a mother hen,” Senku countered.

“At least I care about my teammates. You, on the other hand, would set this entire school on fire just to prove a scientific point.”

“If it meant advancing science, maybe!”

At that, Ukyo—who had been quietly observing—finally intervened. “Alright, alright, I think we’re losing focus here.” He stepped forward, rubbing his temples. “You two do realize there are other rooms in the school, right? Ones that aren’t already occupied?”

“I already checked.” Tsukasa crossed his arms. “None are large enough for what we need.”

Senku scoffed. “And I need this space because—”

“We know,” Gen interjected, holding up a hand. “Senku needs this space for his delicate, genius, scientific experiments, and Tsukasa needs it so his club doesn’t end up breaking bones in a broom closet. We’ve all heard the arguments, but has either of you actually come up with a solution?”

There was a long silence.

Senku and Tsukasa both opened their mouths, then promptly closed them again.

“Thought so,” Gen grinned. “Now, why don’t we stop screaming at each other like a soap opera and try to—oh, I don’t know—negotiate?”

The two rivals locked eyes, the air between them thick with stubbornness.

Tsukasa exhaled. “Fine.”

Senku sighed. “Fine.”

Gen clapped his hands. “Great! Now, let’s find a way to make this work before one of you ends up committing actual murder.”

Outside, Ryusui smirked. “Five bucks says they start arguing again within the hour.”

Kohaku chuckled. “You’re on.”

Chapter Text

Asagiri Gen was a man of opportunity.

He prided himself on his ability to read people, to analyze situations, and most importantly, to capitalize on them. So the moment he saw the absurd, drawn-out battle between Senku and Tsukasa over the club space, he knew.

This was not just a battle, this was something deeper. 

Which meant? Gambling potential.

Thus, in a dimly lit cafeteria, Gen gathered a select group of conspirators. He sat at the head of the table, hands folded like a seasoned war strategist, eyes gleaming with mischief. Across from him sat Taiju, Chrome, Kohaku, Yuzuriha, Ukyo and Ryusui—each drawn in by the promise of something truly outrageous.

“Alright, listen up.” Gen’s voice was hushed but dramatic, ensuring he had their full attention. “I propose... The Senku-Tsukasa Wager.”

A pause.

Kohaku, unimpressed, crossed her arms. “That’s dumb. They quite literally hate each other.”

Gen smirked, tapping his fingers against the table. “Are they?” His voice dripped with amusement. “Or is this the tale of unresolved tension disguised as rivalry?”

A beat of silence passed.

“...Senku did wake up at five in the morning to just to be the first one to claim the club space.” Taiju pointed out, rubbing his chin.

“And Tsukasa is actively countering him.” Ukyo murmured, thoughtfully.

Chrome narrowed his eyes. “That’s... suspiciously relationship-coded.”

“EXACTLY,” Gen clapped his hands, delighted. “Which is why we're monetizing it.”

Kohaku groaned. “You’re ridiculous.” 

“Am I?” Gen raised an eyebrow. “Or am I the only one brave enough to acknowledge the truth?”

Another long pause.

Then—

Slam.

A fat stack of bills landed on the table.

“I’m in!” Ryusui declared, grinning like a wolf scenting prey.

Gen’s smirk deepend. “Knew you would be.”

Yuzuriha, ever the moral compass, frowned. “Wait, wait, wait. How does this even work?”

“Simple,” Gen said, producing a notepad from seemingly nowhere. “We each place bets on when Tsukasa and Senku realise they're hopelessly obsessed with each other.” He scribbles it down on the notepad, tongue peeking through his lips in determination.

Kohaku narrowed her eyes. “You make it sound like it's inevitable.”

Gen tilted his head. “Isn’t it?”

Yuzuriha stifled a giggle.

Chrome still looked unsure. “And what counts as... ‘realising’?”

“Fantastic question!” Gen tapped his pen against the paper. “We have multiple categories—who realizes first, who confesses first, how long it takes, and, my personal favorite, how it actually happens.”

Yuzuriha clapped her hands together. “Oooh, that’s interesting. What if they confess but in a super roundabout way?”

“Then we’ll have a subcategory for that,” Gen reassured her.

Ryusui leaned in. “And who decides what counts?”

“I do, of course, Ryusui-chan.” Gen’s grin was downright sinful.

Ukyo raised his brows. “That seems rather unfair.”

“Would you rather Senku determine it?”

A collective shudder passed through the group.

 “...Alright fine,” Kohaku relented, “When’s the deadline?”

Gen’s smirk is diabolical.

“The deadline is till graduation.”

Chrome widened his eyes, voice kicking up a few octaves. “The entire year?! That long?”

“Well, of course,” Gen sighed, “As much as I hope for those two to look beyond their differences, they are quite dense, especially my dear Senku. And besides, won't it be free entertainment to watch them tiptoe around their feelings for the entire year?”

“Huh, true.” Ryusui cocked his head.

Another silence streched between them as the weight of the gamble settled in.

Yuzuriha leaned forward. “I’m calling it now—Senku, completely oblivious until someone spells it out for him.”

Kohaku groaned and slapped down a 1000 yen bill. “Put me down for ‘Tsukasa confesses in some noble, dramatic way.’”

Ukyo sighed. “This is ridiculous.”

“But you want in, don’t you?” Gen waggled his eyebrows.

Ukyo hesitated for a full second before pulling out his wallet. “...500 yen on Senku realizing it first.”

“What?! That's bullshit! I'm putting down 600 yen on Tsukasa realising it first.” Chrome countered, for some reason.

And from there their blanket of silence was over thrown with all of them making absurd claims and placing bets—madness, is what one could use to describe them. That's what the others sitting on other tables thought. 

Gen just grinned, watching his empire flourish.

-

Senku knew how to share. He wasn't that immature.

Though he couldn't say the same for Tsukasa.

Sure, there was a temporary truce between them, as absurd as it was—this was originally his place, and who even gave the Student Council the bright idea to merge two clubs that couldn't be more different in all aspects? He would've co-operated with Tsukasa, really, ten billion percent but that man had striked first so it was only fair that he retaliated with the same intensity.

It had been a mere three days since their outburst in the club and the others had intervened and asked them to calm down and possibly, find a solution.

And there was one: the Athletic Club waddling back to their own club space and leaving Senku alone.

Of course, Tsukasa didn't accept that.

(The others, despite their ongoing bet, had dreamed that the two would ceasefire,

And they had, for a while, at least. 

Except that was just them sitting on opposite sides, steaming in unbridled rage and heated glares while the other meticulously continued with their routine around them.

That dream, however, lasted only till lunch break.)

A week, and what a horrendous week it was.

It started off relatively civil. Well, as civil as a discussion between Senku and Tsukasa could get. The others had warned them (read: an exasperated Ukyo and a fed-up Kohaku)—no yelling, no excessive pettiness, just pure negotiation. Honestly, it was their fault, they had assumed the two would have sensibly agreed and maybe, just maybe, made peace. 

It started small. Almost unnoticeable.

In their so called peace-treaty, the space had been evenly divided between both the clubs. Despite everything, the Science Club did have a significantly larger space but that was necessary with the amount of experiments they used to conduct, in an hour nonetheless.

Tsukasa had walked into the club and had found his side of the space overrun by Senku’s ridiculous science projects. Test tubes, flasks, a Bunsen burner (that had no business being here), and a suspicious-looking white powder were strewn across the table.

Tsukasa, ever the picture of patience (or so he claimed), took a deep breath and moved exactly half of the items to the other side. Exactly.

Senku, of course, immediately noticed when he walked in later.

“Oh? How generous of you,” he said flatly, examining the precisely aligned boundary line. “What’s this, some kind of territorial piss-marking? Should I start measuring the air quality on your side too?”

“I’m merely making sure the space is fairly divided, as agreed,” Tsukasa replied smoothly, sipping his tea like he wasn’t incredibly pleased with himself.

Senku narrowed his eyes. “You measured it with a ruler, didn’t you?”

“I wouldn’t want to intrude on your sacred scientific process, after all.”

And just like that, the passive-aggressive game escalated at a speed only rivaled by scientific progress itself.

By the afternoon, Senku rearranged their desks so that Tsukasa’s seat was exactly two degrees off from its usual placement, just enough to throw off his muscle memory. Tsukasa didn’t even blink, simply sitting in it like normal, but he knew. He knew, and that was enough.

So, in retaliation, Tsukasa subtly increased the weight of Senku’s chair by taping small weights underneath it. It wasn’t noticeable at first—until Senku sat down, frowned, then glared daggers at Tsukasa, who merely smiled like the devil in disguise.

The club members, by this point, were already exhausted.

“I swear, if one of them starts claiming more oxygen molecules than the other, I’m leaving,” Chrome muttered, watching the silent war unfold.

Gen, ever the opportunist, simply hummed. “Oh, but my dear Chrome, this is quality entertainment.”

Kohaku pinched the bridge of her nose. “It’s day one. We’re not even past lunch, and they’re already acting like divorced parents trying to one-up each other over custody arrangements.”

By the end of the day, the clubroom had transformed into a passive-aggressive battlefield, with both sides maintaining a perfectly even split down the middle. Even the air felt tense.

It only went downhill from there—

Senku needed the whiteboard for equations.

Tsukasa needed it for scheduling training sessions.

The obvious solution? Take turns. The real solution? Fight to the death.

Both walked into the clubroom at the same time, markers in hand, and immediately started writing—over each other’s work.

“Oh, I see, you’re just gonna write over my formulas?” Senku said flatly, watching as Tsukasa casually erased his detailed calculations.

“I assumed you were done,” Tsukasa replied, as if this was perfectly reasonable.

Senku, smiling through gritted teeth, erased Tsukasa’s schedule and rewrote his formulas.

Tsukasa immediately erased them again.

This went on for five full minutes. The others sat in horrified silence.

“Should we stop them?” Yuzuriha whispered.

“No,” Gen said, observing the chaos. “Let’s see how far they take this.”

-

By midweek, the clubroom was a warzone.

Senku locked the cabinet where Tsukasa kept his training gear.

Tsukasa unplugged Senku’s experiment mid-trial.

Senku “accidentally” misplaced Tsukasa’s workout schedule.

Tsukasa switched the chemicals in Senku’s labeled jars, leaving the scientist to discover his carefully calculated solution was just water.

The final straw for Chrome? His desk was collateral damage. His poor desk, where he sat, minding his business, suffered a spilled beaker and a dumbbell smashing into one leg, leaving it wobbly and untrustworthy.

“I am losing my mind,” Taiju groaned.

Chrome, cradling his broken desk leg, muttered, “I think we all are.”

-

By Friday, the tension was unbearable.

The clubroom was unusable. Supplies were mysteriously missing, chairs mysteriously moved, the air so thick with passive-aggression that Gen swore he could taste it.

The moment Senku and Tsukasa entered, Yuzuriha slammed her hands on the table.

“That’s it!” she yelled. “We need to talk.”

Senku and Tsukasa, frozen mid-glare, turned to her.

“You two,” Taiju growled, “are driving us insane.”

Gen smirked. “Oh, I don’t think it’s ending anytime soon.”

Chrome groaned. “It better end. You guys are ruining the club.”

“You’ve made an enemy of peace!” Yuzuriha added.

Tsukasa sighed. “That’s dramatic.”

“Oh, I’m dramatic?” Chrome gestured wildly. “You two just spent twenty minutes arguing over chalk!”

Senku shrugged. “I had to prove a point.”

“That you’re both insufferable?” Gen supplied helpfully.

“We demand you have an actual truce,” Taiju said firmly. “Not this ‘fake peace’ nonsense where you just mess with each other instead of yelling.”

Senku and Tsukasa exchanged looks.

For a moment, there was silence.

Then Tsukasa smirked. “Fine. An actual truce.”

Senku crossed his arms. “Yeah. Whatever. I don’t have time to waste on this.”

The others sagged in relief.

…Until they turned back to see Tsukasa and Senku smirking at each other.

Gen groaned. “Oh, they’re still going to mess with each other, just less obvious.”

Chrome flopped onto his broken desk. “Kill me now.”

Ryusui, counting money, grinned. “So, bets on how long this truce lasts?”

Senku and Tsukasa didn’t even try to deny it.

The war was over.

But the battles? Oh, the battles had only just begun.