Work Header

don’t trust an atom (they make up everything)

Chapter Text


“Oh shit,” was the first thing Katsuki heard upon waking. He snapped out of the last tendrils of unconsciousness faster than he ever had before, bolting upright to squint across the dim room. The door was hanging half-open, an unfamiliar shape blocking most of the light that fell through the entrance. “Uh, sorry to interrupt,” said the interrupting person.

A grumble came from beside Katsuki. An arm, sprawled across his waist, tugged sleepily at him like its owner was trying to pull him back into bed. Katsuki ignored it and glared at the intruder. “Fuck you want?”

“Hey man, it’s my room too,” the guy rejoined. He finally came inside, pushing the door shut behind him and crossing the room to the bed on the other side of the wall. “I’m your roommate, remember?”

Katsuki groaned and dropped back to his sheets. “It’s barely the first day of the semester, have you been partying all fucking night? No, don’t answer that.” He glanced over to his bedmate who was currently, slowly, squirming back to wrap himself around Katsuki. “Ugh, fuck off.”

No reply, just mossy green curls shoved up against Katsuki’s face. He sneezed at the attack and glared down. “Deku,” he growled.

There was a clatter from his roommate’s side of the room. “Oops,” he said. A loud rustling. “So’s that your boyfriend?” the roommate asked cheerfully.

“None of your business,” Katsuki snapped. “Now fuck off before you wake him up.”

“I dunno man, you’re being plenty loud enough to wake him up.”

Katsuki reached down, hand searching past the sheets and into the air before his fingers found the leather of one of his boots. He hurled it and was rewarded with an alarmed squawk.

“Alright dude, okay! I’m leaving, anyway.” There were a few more too-loud noises but finally, his roommate left the dorm again, trailing wires from the entire Playstation he was lugging with him.

As soon as the door clicked shut, Deku’s head popped up, hair wild and sleep marks creased into one cheek. He squinted blearily at Katsuki. “Time’s it?” he slurred.

“Fucker. I knew you were awake.” But Katsuki fetched his phone from its charger cable on the bedside table and swiped at the screen. “It’s ten after five.”

Deku yawned, squeaking out a tiny noise that Katsuki absolutely did not find adorable. He sat up, pulling the blanket from both of them with the movement and stretching out his arms. The blanket pooled around his hips, and Katsuki eyed his bare torso with interest. It might be disgustingly early in the morning, but Deku’s abs were nothing to frown at. “Good morning!” Deku chirped, finally done with his weird morning routine stretch. He leaned down to kiss Katsuki but Katsuki planted a hand in his face to stop him.

“I ain’t kissing you with your ass breath,” Katsuki warned.

“That’s not what you said last night,” said Deku. He just giggled when Katsuki pinched his hip. Katsuki wondered why he had been cursed with a boyfriend who was a morning person. Well, Eijirou was too, but at least he made Katsuki tea in the mornings. Deku always burned tea; how, exactly, he did so was a mystery to everyone.

“Alright, I’m gonna head out,” Deku declared. “I’m meeting Kiri at the gym in twenty minutes.” He swung one leg over Katsuki, straddling him for a brief moment before moving off him and hopping onto the floor.

Katsuki shamelessly watched his ass in his stupid yellow boxers as he tugged on the pants, shirt, and shoes that had been thrown to the floor last night. So maybe they had gone a little overboard, but Deku had spent most of winter break at a temp job and Katsuki had stayed with Eijirou and his moms, so they hadn’t spent much time together.

As soon as Katsuki had moved his items back into his dorm yesterday - and ignored his new roommate that Housing had assigned to him because he’d scared off his roommate from the fall semester - he’d texted Deku to come over. Shouto, who usually would have come with Deku, had apparently gone to see Eijirou. That was fine; they all couldn’t have fit in his shitty dorm bed anyway.

“So who’s your roommate?” Deku asked as he pulled on his socks and shoes. He glanced up at Katsuki, but it was still dark enough that his face was barely visible. Katsuki hoped he’d put on his shirt backwards. He’d look fucking hilarious. Maybe Eijirou would take a picture and send it to him.

“Dunno,” he said and yanked the discarded blanket back up over his torso. Shouto had gotten it for him, but not like any normal person; no, Shouto had crept up on him in the middle of the night last fall, tossed it on him with a note that said ‘Don’t freeze to death’ and then left. Shouto was a fucking weirdo. He was lucky he was hot.

Deku looked very disapproving, maybe. It was hard to tell in the darkness. “You don’t know your own roommate’s name? You met him yesterday.”

“Don’t care,” Katsuki clarified. He slapped his phone back to the bedside table. “He’s annoying.”

“He looks kinda familiar,” Deku mused. He finally stood, rummaging through Katsuki’s desk to find his wallet and phone. “I think we might have taken our anatomy and physiology course with him last semester.”

Don’t care,” Katsuki repeated.

“Hmm, you’d better be nice to him.” Deku approached the bed again and bent down to kiss Katsuki’s forehead. Katsuki glared at him. “He’s going to have to put up with you for the whole semester. Don’t scare him off like your last one.”

“My last roommate was a copycatting bitch who tried to steal my homework,” Katsuki growled. “He deserved to have the shit scared out of him.”

Deku patted his cheek fondly. Katsuki tried to bite his hand. “Well, I’m off,” Deku said brightly and headed for the door. “See you later! Say hi to Shouto for me.”

“What?” Katsuki squinted after him. “Deku! What?”

Deku waved cheerfully and shut the door behind him. Katsuki scowled after him and considered for a moment texting Eijirou to find out what he meant, but he was too tired to deal with Eijirou’s emoji-laden replies. Shouto wasn’t even worth trying; he wouldn’t be awake until five minutes before his first class started.

Katsuki huffed and rolled over to fall back asleep.


Making his way into his first class of the day, Katsuki was greeted by the sound of a desk crashing to the floor and a massive body hurling at him.

“Katsuki!” Eijirou bellowed, probably bursting the eardrums of the other few students who had arrived early. Katsuki allowed him to wrap his arms around him for a good five seconds before he shoved out of his grip.

“Alright, that’s enough. You act like you didn’t steal my schedule so you could get the same class as me.”

Eijirou grinned, sharp teeth glinting. That, coupled with his enormous build, would be intimidating, but the softness of his face and kind eyes more than made up for it. “I’m just happy to see you! Come on, sit next to me!”

Katsuki wasn’t sure that was the best idea, but he followed Eijirou to the centre of the classroom anyway. Eijirou easily lifted the heavy desk and dropped into it, patting the desk beside him expectantly. He was wearing an awful crop top shirt with the words Red Riot printed across it, and the line of his hips was visible just beneath the ragged edges. It was annoyingly attractive. It did not, however, make up for the awful red Crocs he was wearing.

Katsuki sighed and sat down. He pulled out his computer and notebook, arranging them on his desk and aware that Eijirou was watching him intently the entire time.

“What?” he finally snapped, and Eijirou beamed in reply.

“You just have a particular way you set up your stuff, it’s cute.”

“I am not cute.”

Eijirou leaned over to ruffle his hair. He would have lost his damn hand if Katsuki had any weapon within range. “You are,” he cooed. Yeah, he’d been spending far too much time with his moms. He needed to move out of their place.

“Fuck off,” Katsuki snapped, but Eijirou didn’t reply this time. His gaze fell past Katsuki to the door and his face lit up.

“Oh my god!” The desk went flying once again as Eijirou tore across the room to the two students who had just entered. “Mina! Hanta!”

“Kiri!” they both shrieked, and tackled him with hugs.

Katsuki sighed and opened his laptop. Eijirou’s friends were as loud as he was, but multiplied by five times or so when they were all together. He tuned them out as they exchanged greetings and chattered, changing topics like they were tossing a hot potato from one to the other.

“Hell no,” Katsuki warned Eijirou when the trio began to approach him. “If they sit here, I’m moving. I don’t want you loudmouths next to me when I’m trying to pay attention.”

“You’re so studious,” said Eijirou reverently, but then picked his desk up and sat down in it again, entirely ignoring Katsuki’s threat. “You guys can sit over here!” he invited, pointing to the desks on the other side of him. Both of his friends toppled into the desks, no notebooks or pencils anywhere in sight, and began talking again.

Katsuki glanced around at the other ten or so students that were in the room so far, and wondered if he could possibly get away with murder in public.

“Here, babe,” said Eijirou. Katsuki glared at him and snatched the earbuds he was offering.

“If you talk during class, I’ll shove these down your throat,” he threatened.

Eijirou grinned and turned back to his friends. Katsuki huffed and put in the earbuds, linking them to his computer to listen to a pounding beat that rattled his skull until the class began.

Their professor arrived exactly two minutes before class began. He banged around at the podium, bright blond hair almost glinting with the sun creeping into the small windows of the room. “Alright, class!” he bellowed at exactly eight, and Katsuki tugged out his earphones. Well, at least he wouldn’t have a problem hearing in this class. “I’m Yamada Hizashi, your teacher for this literature class! It’s a core class, so you don’t have a choice but to be here, but just try your best!”

Katsuki wouldn’t try his best. He’d do his best. He’d fucking rule this class.

“Katsuki,” Eijirou whispered. Katsuki stared straight ahead at their professor, who was scrawling his name in kanji across the blackboard. “Babe. Kats. Bakubabe.”

Heaving a deep sigh, Katsuki yanked an extra notebook from his bag and slapped it into Eijirou’s chest. He could feel Eijirou’s grin aimed at him.


“Be quiet,” Katsuki hissed.

Eijirou beamed harder, but finally bent his head over the notebook and began scribbling in it.

Katsuki, maybe, perhaps, liked that he was sharing a class with Eijirou, even if that would come with the responsibility of forcing Eijirou to study. Well, they could study like they did in their class with Shouto and Deku last semester. Sex was a great bribe.

Now who wasn’t paying attention? Katsuki glared at Eijirou for daring to remind him of sex, then focused back on the professor. This was going to be an interesting class.


“Headed to your next class?” Eijirou asked as Katsuki slipped his laptop and notebook into his bag. “Whaddya have?”

“Statistics. Another fuckin’ core class.” Katsuki caught Eijirou’s desk when Eijirou stood and it began to tip once again.

“I have Systems Programming!” said Eijirou. He followed Katsuki as he left the room. “It’s supposed to be super hard, though, so I’m going to a study group right afterwards. Maybe I’ll make some new friends!”

Someone in the hall stared admiringly at Eijirou’s visibly toned stomach below the ragged edges of his crop top, but they flinched away when they noticed Katsuki’s glare. Yeah, you’d better be scared, fucker. He’s mine.

“Got to pee!” Eijirou announced, and he headed for the bathroom at the end of the hall. His spiked red hair almost brushed the top of the doorframe as he went through.

Katsuki glanced at his watch, considered his next class which was thirty minutes away and in a building halfway across campus, and decided he had enough time. He followed Eijirou into the bathroom.

“Okay, but I do actually have to pee,” said Eijirou when Katsuki shoved him into the largest stall in the bathroom. Katsuki locked the door and pushed him up against the wall. This one was at the end of the row of stalls. Katsuki had had a class in here last semester, so he and Eijirou had...frequented this bathroom.

“You can go later.” Katsuki slid both hands up the loose edge of Eijirou’s shirt, fingers pressing into the ridged muscle and curls of dark hair that trailed down below the line of his jeans. His skin was warm and soft and it trembled beneath Katsuki’s touch.

“Don’t you have class in like twenty minutes - ?” Eijirou’s protest was cut off by his own sharp inhale as Katsuki reached down and palmed over the front of his jeans.

“You gonna shut up and let me do what I want?” Katsuki popped the button on Eijirou’s jeans.

“Uh,” said Eijirou, pupils blown wide.

Katsuki grinned at him and slid down to his knees. “Yeah, that’s what I thought.”


“‘Say hi to Shouto for me,’” Katsuki muttered under his breath, repeating what Deku had told him with a grin that morning, as he eyed the person that had just entered the classroom. “Deku knows all our schedules, doesn’t he? Little shit.”

“Hello,” said Shouto as he approached. He looked like he’d just rolled out of bed - and he probably had, if this was his first class today. He was gripping a large coffee like it was the only thing keeping him sane and had another small cardboard cup in his other hand.

Katsuki narrowed his eyes at Shouto as he slid into the desk beside Katsuki. “I get no peace, huh?”

“Izuku said to say good morning,” Shouto said mildly. He handed the smaller cup to Katsuki. “Izuku is wrong. Mornings are not good.”

Katsuki sipped from the cup. Fuck. If there was one thing good about Shouto’s coffee obsession, it was that he never forgot what others liked to drink as well. This hot matcha tea was perfect not only to revitalise Katsuki, but also to wash the lingering taste of Eijirou off the back of his tongue.

Katsuki startled when he felt a cool finger poke his neck. “Fuck! What?”

Shouto tilted his head and considered his throat curiously. “You have three hickeys,” he said.

Katsuki swore and pulled out his phone to flip the mirror and examine his own neck. Sure enough, two fading bruises were tucked into the dip of his collarbone and a fresher, purpling one was blooming over his jugular. “Shit. Fucking Deku and his biting kink.”

“That new one is definitely from Eijirou,” Shouto pointed out. “His teeth are much sharper.”

Katsuki glared at him. “You can’t talk. All three of you shitheads like to bite.”

Shouto turned away haughtily as he lifted his cup to his lips, but notably didn’t argue. Katsuki snorted. He had a feeling this class was going to be a little calmer than his one with Eijirou.


Katsuki glared when Shouto and Deku slid into the booth opposite his seat. Deku looked harried, his hair wild like he’d been running his hand through it nonstop - and he probably had been, knowing him - but Shouto seemed unconcerned, face placid as he sipped from a thermos. “You’re late,” Katsuki accused.

“We had to stop and get coffee,” said Shouto.

“It’s decaffeinated,” Deku explained when Katsuki squinted at him. He picked up a menu and frowned intensely at it as he read. Katsuki didn’t know why he bothered. They frequented this restaurant, as it was the only good curry place within walking distance of Shouto’s and Deku’s apartment, and they all had the menu practically memorised by now.

Katsuki scoffed and reached across the table to pluck the thermos from Shouto’s hand. “You’re going to have a heart attack from how much coffee you drink.”

The look he received in return was withering. “Give me back my coffee,” Shouto said icily.

Unscrewing the lid of the thermos, Katsuki maintained eye contact as he chugged the last dredges of Shouto’s coffee. It was fucking awful. Katsuki wasn’t a fan of coffee, and certainly not black coffee with only a splash of milk, but he wasn’t going to let on. He slammed the thermos to the table and shoved it back to Shouto.

Shouto might like to think that he remained neutral at all times, face expressionless, but right now, he was definitely pouting. He grabbed the empty thermos and frowned at Katsuki with furrowed eyebrows. “I’m breaking up with you,” he decided.

Deku, who had been ignoring them both the entire time, reached over without looking to consolingly pat Shouto’s hand. “Babe, we’ve talked about breaking up with people over your coffee addiction.”

“He drank mine,” Shouto complained. “He deserves to have one less boyfriend. Izuku, you should break up with him too.”

Deku laughed. “Shouto, I’m not breaking up with Kacchan. Who would pay for our meal?”

Crossing his arms, Shouto looked off into the distance, a stubborn set to his mouth. “I can. I’m rich.”

“Yeah, all right, Daddy’s boy,” said Katsuki, and leaned over once more, but this time to steal Deku’s menu. Shouto scowled at him, either for the insult or that he’d dared interrupt Deku’s musings over his food choice. “I already ordered for you two fuckers.”

“Thanks, Kacchan!” Deku chirped. “What’d you get me?”

“I will hate whatever you got me,” said Shouto, clearly still offended.

Katsuki ignored him, slapping the menu down on the empty seat beside him and squinting at Deku. “Alright, you were frowning at that thing for five minutes. You might be slow as fuck at making decisions, but never that slow. The fuck’s wrong?”

Deku’s face and cheerful facade fell, caught out. He glanced anxiously at Shouto, who just blinked back at him, and wrung his hands in the most Deku motion ever. “I…I dunno. I guess so, Kacchan.” He hesitated, and Katsuki was glad that at least he hadn’t gone off about how he was happy Katsuki was asking how he was doing, as he had done many times before.

“Spit it out, nerd.”

Deku whined and propped his elbows on the table, burying his face in his hands. “I just - it’s first day jitters, right? My classes are all just really intense and it’s only the first day. I had Microbiology lecture and lab, Medical Terminology, and Pathophysiology with lab today and they’re really hard.” His face finally popped back up, expression conflicted. “Not that I’m not up for hard classes, I just…all during class today, I could only think ‘What if I’m making the wrong choice?’ Like…I’m dedicating myself to this major but what if it’s not what I really want? I don’t know.”

Katsuki considered what Eijirou might say if he was here and not helping out at his moms’ restaurant tonight. Everyone goes through a crisis about their major, maybe. Or perhaps he’d reassure Deku with a It’s okay to be unsure! and spout off some wise bullshit that would make Deku instantly feel better and able to make a decision.

Well, Katsuki wasn’t Eijirou. He picked up the menu beside him and rapped Deku on the head with it, who yelped and looked at him with wide eyes. “Stop spiralling. If you’re so worried about it, explore some other options.”

Deku blinked and swiped at his eyes. They’d welled up, either from the surprise of the menu attack or, more likely, from what Katsuki had said. “Thanks, Kacchan,” he said, voice moist.

“Ugh,” said Katsuki, and threw a napkin at him.

Shouto patted Deku’s shoulder. “Yes,” he said. “But also consider that you have wanted to be in the medical field since you were five. If it is what you’ve always wanted, stick with it and you’ll get through it.”

Deku blew his nose into the napkin. It should have been gross, but instead, it sounded like a kitten having an asthma attack. He sniffled loudly. “Thanks, Shouto. I’m so glad you two are my boyfriends.”

It was probably a good thing Eijirou wasn’t here. He was a sympathetic crier. If he saw Deku’s wobbling jaw and glassy eyes, he’d starting bawling too, and they’d have a crying fest in one of their favourite restaurants.

“Shit,” said Katsuki, instead of replying. He’d had enough of this emotional discussion. “Where the fuck’s our food?” He waved angrily at one of the servers across the room. She maintained eye contact for half a second, then scurried back into the kitchen. Wimp.

Shouto procured another thermos from literally nowhere and offered it to Deku. “Want some coffee?”