Everyone knew the secondary gender trinary was bullshit. Secondary genders didn't mean a thing, and even if they did mean something to other people - like his friends, or parents, or doctors, or teachers - they still meant nothing to Bakugou Katsuki, which resulted in a zero-sum game, as far as he was concerned. The secondary gender trinary was like your blood type, or your zodiac sign. Something that boring people talked about when they had no real accomplishments to their name. As far as he was concerned, one’s secondary gender was an interesting but largely irrelevant bit of trivia. Alpha, beta, omega, none of it mattered, except to pathetic people with nothing better to think about. Secondary genders didn't mean a goddamn thing to Katsuki. They couldn't mean anything, because if they did, then Bakugou would never have what it took to be a true hero.
The secondary gender trinary was the only things separating him from heroes like All Might, Endeavor, even fucking Best Jeanist. Heroes like Eraser Head or Present Mic didn't share his secondary gender, either. But that was fine, because it didn't matter, despite what the media, popular culture, and commonly accepted wisdom stated to the contrary. Bakugou knew this because he knew himself. He knew he wasn't some pathetic weakling or simpering fool. When he wanted something, he got it. When he thought something, he said it. None of the supposed weakness or desperation attributed to his secondary gender would ever gain so much as an inch of ground in the battlefield of his life.
Still, if people saw Bakugou’s behavior as evidence of an individual expressing qualities generally equated with an alpha, that was fine with him. After all, it would be no worse than if people went around assuming his blood type was AB or some shit. Besides which, who fuckin’ cared what they thought?
Well. Maybe he cared a little.
It seemed like most people were obsessed with knowing the secondary gender of everyone they knew. Katsuki resented this - sometimes people would point to him and say shit like, “Of course he’s so strong and aggressive. He’s an alpha.” Bullshit! He was awesome because he’d worked his ass off from day one, not because of some stupid biological programming. He was determined to be the best, and it was infuriating that people - especially the media, after the disastrous conclusion to the UA Sports Festival - would write off his skill, determination and work ethic by ascribing it to a secondary gender they'd only assumed based on circumstantial evidence! Fucking. Bullshit. Acting like an alpha must mean he is an alpha, which explains why he's so fucking good at acting like an alpha. Fuck! What sort of twisted logic was that, anyway?
He couldn't even escape the theorizing at school. Being high school students, Bakugou and his classmates were reaching the point of maturity where their secondary genders were becoming more obvious, and locker room talk began to center around the topic of who in their class would be likely express certain characteristics. The whole idea of it was fucking gross, in Bakugou’s opinion. Everyone deserves their privacy, a person should be able to exist without having people follow them around, theorizing about their secondary gender. Of course when it came to making verbal predictions of who would present which characteristics, the repeat offender was grapes-for-brains, but as the year wore on Katsuki found himself encountering more and more conversations about the trinary. Even in public spaces where it should be highly discouraged. Fuck. Bakugou shouldn’t have to be the one telling people when their public behavior is inappropriate. But somehow, he seemed to be ending up in that situation more and more often. Like the time Kaminari told Kirishima what he’d learned from spying on the girls as they filled out paperwork for their annual health checks.
“I can't believe it!” Kirishima bellowed, showing no recognition that he was using his outside voice in an indoor space. Library windows rattled as Kaminari jumped back, not expecting quite this reaction to the juicy bit of gossip he'd gleaned earlier.
“I'm just telling you what I saw,” Kaminari protested.
Kirishima shook his head in amazement. “Yaoyorozu never struck me as the alpha type,” he declared, gesticulating wildly. “Hell, I would have put money on her being a beta!”
Kaminari shushed him, though Bakugou figured it was a moot point. The whole library had probably overheard the exchange. Not that he cared - he wasn't the one embarrassing himself. But he was starting to tire of their idle chatter. “Oi, rocks-for-brains,” Bakugo growled, tapping his textbook pointedly. “Quit yapping about useless bullshit and answer the fucking question!”
Kirishima looked chagrined. “I was just-”
“Wasting my time,” Bakugou interrupted. “If you and low-watt bulb over here want to gossip and giggle like a pair of nosy old women you can do it on your own time.”
Kirishima appeared properly cowed. He leaned over his textbook, making it about two sentences in before Kaminari commented in a stage whisper, “Turns out Jiro’s an alpha too.”
Kirishima's head jerked up again. “No way!” he shouted, “Seriously?”
“I'm just telling you what I saw on the health check forms,” Kaminari assured him at what had to be top volume.
“Would they lie on their forms?” Kirishima mused in what could nearly be considered an inside voice.
“Why the fuck would they lie?” Bakugou demanded irritably, only to realize, much to his chagrin, that he'd somehow been tricked into joining the conversation. “...the secondary gender trinary is all fuckin' bullshit anyway,” he added, mentally patting himself on the back for the smooth recovery.
Kaminari sighed gustily. “You would say that,” he bemoaned, “We all know you could have any omega you wanted.”
“Maybe,” Bakugou conceded, “But it'll be because I've become the greatest hero of all time,” Bakugou added with a snarl, “and not because of some body odor bullshit.”
“They're pheromones, not anything gross like that!” Kirishima protested, “They don't stink, just… smell funny.”
Maybe to someone like Kirishima, Bakugou thought darkly. But one unique characteristic of Bakugou’s own secondary gender was the inability to smell much of anything beyond surface level smells. Which basically meant that hulked-out alphas reeked fuckin’ constantly. Betas tended to assault the nose to a lesser extent than alphas, and omegas were usually tolerable except when they got close to heat. That was the extent of Katsuki’s smell powers - everyone smelled bad and could use more showers in a day. The worst of it was that alphas and betas could smell things, things like honesty and trust and fear and loneliness, but all Bakugou ever managed to smell served only to remind him of dirty old gym socks.
People with a secondary gender like Katsuki’s didn't have the sense of smell needed to sniff out subtleties. It's why they were expected to rely on others to negotiate. It’s why people with other secondary genders were told to ‘take care’ of people like Katsuki. How could one be expected to survive if they couldn't smell a lie, pick up a whiff of aggression, or recognize the heady scent of arousal?
Personally, Katsuki figured his technique of "explode first, ask questions later" got the job done just fine. He didn't need to smell anyone's pheromones if he could just as easily decide he didn't like their face, or the look in their eyes. And he usually did just fine, thank you. Even if these oh-so-important pheromones all just smelled like body stank to Katsuki. He himself showered several times a day to keep the smell of himself as mild as possible, but others were not so thoughtful. Whatever. His inherited nitro-sweat was at least a convenient excuse for the frequent showers. He’d have a harder time explaining that everyone, including himself, smelled like shit half the time. God, he hated people who refused to shower regularly.
“Do you think Uraraka’s an omega?” Kirishima asked Kaminari, changing the subject.
Bakugou growled and slammed his book shut, rising to his feet. “God dammit, why do I even fuckin’ try ?” he snapped.
“Where are you going?” Kaminari protested, suddenly oh so concerned with their study session.
“To finish my homework in the peace and quiet of my own goddamn room,” Bakugou answered sharply. “Have fun finishing up your gross conversation.”
“Hey wait!” Kaminari protested.
“We can focus on the homework now, really!” Kirishima added.
“Good,” Bakugou dropped his book back on the table with a loud noise. “Question nine.” Mercifully, the rest of the afternoon continued without further mention of secondary genders. None of the three noticed Izuku Midoriya watching them thoughtfully, half-hidden behind a towering stack of books, a slight frown creasing his brow as he considered one Bakugou Katsuki.
Time wore on, and across the school, students began to present ther secondary gender characteristics in earnest. Alphas went into rut, omegas, heat. Excused absences abounded, though most members of class 1-A had yet to produce evidence of their secondary gender. Fortunately for no one, Mineta had devised a plan to identify all the omegas in their classroom. He was explaining the plan to Sero and the other few students loitering in the classroom after lunch but before everyone was expected to be back in their seats.
As per usual, Katsuki was at his desk, arms folded, a look of bland disinterest and vague irritation on his face. He may have looked calm to his classmates, but inside, Katsuki was caught up in a maelstrom of emotion. Regretfully, he was not exempt from the bullshit biological changes that adults saw as a “rite of passage” from childhood to adulthood. As he neared the age of presentation, he was finding it harder to avoid acknowledging his own secondary gender. Gritting his teeth, Katsuki was mostly preoccupied, trying to forget the fact that his mother had called the night before. She had asked if he wanted her to accompany him to his upcoming screening with the family doctor. He did not.
Caught up in the thoughts swirling around inside his head, Bakugou didn't really pay attention to what was going down in the room around him. That is, until Mineta started waving his arms around, making a proper spectacle of himself. That was enough to draw Bakugou back into the conversation, if only to tell the purple-headed bastard to fuck off. He was prancing around, proudly showing off some weird cylindrical object in his hand. Upon closer observation, it looked like a can of hairspray. What the fuck? Bakugou sat up, intrigued enough to listen, at least for the moment.
“Now, this,” Mineta lifted his aerosol can demonstratively, glancing between the few people in the room (most of whom were still pointedly trying to ignore him) and wiggling his eyebrows, “is a little thing I got my hands on last week.” He smirked. “It's from an adult store. It has pheromones in it that will trigger an omega’s rut!” He waved the can tantalizingly. “All we have to do is spray it around the room before the girls get back, so that when class starts-”
Katsuki had heard enough, standing suddenly. “You can do what, rape our classmates because you can't keep your pathetic beta dick in your fuckin’ pants?” Bakugou interjected, seeing red. He marched towards Mineta menacingly, palm extended. “Hand it over.”
“No way!” Mineta clutched the aerosol can to his chest defensively. “Do you know the trouble I went through to-?!”
Bakugou let a few small explosions dance across his fingers, feeling a white-hot rage building up inside him. “I don't fuckin’ care.”
Mineta scowled. “It’s a harmless prank!”
“Harmless if you're not a fuckin’ omega,” Bakugou countered. He stared at Mineta, eyes sharp as flint. “Don't make this difficult,” he snarled, and lunged forward, ripping the can from Mineta’s feeble grasp. Just as he was about to toss it across the room into the trash can, Mineta made the stupid decision of trying to grab it back. Instinctively, Katsuki incinerated the can, which exploded in a whoomph of sickly-sweet scent that smelled like the taste of almost-burnt marshmallows. The contents of the aerosol coated him, filling the air with the smell of a cotton candy stand that had caught fire. Bakugou swore creatively and effusively, running to open windows and air out the classroom.
This was how the next classmate to return to the room found them - Mineta, howling pitifully about the loss of his beloved aerosol. Sero and Kaminari, exchanging awkward glances. Bakugou, throwing open windows, trailing expletives wherever he went.
Ashido was the first one to arrive post-incident. “What the hell?” she exclaimed. “What happened here? And why does Bakugou smell like the Wonka candy factory exploded all over him?”
“It fucking did,” Katsuki growled, before stopping to point at Ashido. “You an omega?”
Ashido scowled. “Not that it's any of your business, but no.”
“Good,” Katsuki said. “I’m going to go take a long-ass shower, you make sure this room gets aired out. Grapes-for-brains thought it would be a nice prank to fill the room with heat-inducing pheromones.”
Ashido glared at Mineta, her normally warm, inviting gaze growing cold and dangerous. “You didn't.”
Katsuki pushed past Ashido. “I need to scrub this candy stank off me,” he growled. “If Aizawa asks why I’m late, blame the purple shithead.”
He hurried down the hallway, trying not to spread the odor around more than was absolutely necessary to get him to the showers. He made it to the locker rooms and, after a split second of hesitation, went into the shower while still wearing his clothes. After all, they smelled as bad as he did, so he washed them first, then peeled them off to wash his body.
The water was warm, but Bakugou was boiling, practically incandescent with rage. How dare the purple snot attempt to out his classmates like that? It was more than just rude, it was infuriating. Bakugou slammed his fist against the shower knob, cutting off the stream of water, panting heavily. The room was filled with hot steam, and the thick moisture that hung in the air felt almost as suffocating as the awful sweetness of Mineta’s “prank” substance.
Katsuki growled low in his throat as he towelled off, reluctantly tugging on his gym clothes because who the fuck stashed an extra set of clothes at school? Not Katsuki. He also wasn't about to ask if there was some secret stash of extra uniforms lying around here, either. He didn't particularly like his uniform anyway. It hung loosely on his frame for a reason, and that reason was to minimize sweat. While he could actively excrete large amounts of nitroglycerin from the palms of his hands, it didn't change the fact that his skin excreted, all over his body, trace amounts of nitroglycerin. And that wasn't exactly a stable substance, so from a young age Bakugou’s father had taught him how to dress to minimize sweat and found him a pretty awesome spray-on antiperspirant that he used quite liberally.
The steam clouds were finally dissipating, though the room remained uncomfortably warm as Bakugou began towel-drying his hair, scowling at the empty locker room like he suspected it wanted a fight.
Across the room, the door to the hallway opened and Kirishima poked his head inside, catching sight of Katsuki. “Yo,” he said hesitantly. “Mister Aizawa sent me to find you.”
Bakugou paused, staring blankly at Kirishima. “You found me,” he said slowly. “Is that fucking all?”
Kirishima let himself into the locker room, shutting the door and sinking down onto one of the benches in the middle of the room. “Are you okay?” he asked hesitantly.
“Yes. Why?” Bakugou glared at Kirishima. “Do I not look okay?” his heart pounded furiously in his chest. Hard-headed freak, looking down on him like he needed to be fucking comforted.
“Kaminari told everyone that you confronted Mineta,” Kirishima explained, “And then ran away, which didn't sound like you, so we got worried, and…” he shrugged expansively, as if to say ‘here I am’.
Bakugou growled under his breath. His classmates were all a bunch of nosy motherfuckers. “I just wanted to wash away the stank Purple Balls put on me before it ended up fumigating the whole fucking classroom,” Bakugou explained slowly, as if speaking to a small child. A bead of water trickled down his forehead. Why was this room so fucking hot?
Kirishima but his lip. “For what it’s worth, Mister Aizawa sent Mineta to detention,” he said. “And he said he was proud of you.”
“I don't need his approval,” Bakugou snapped, wrapping the towel around his neck and slathering his underarms with a generous coat of antiperspirant. “I know when I did the right thing, I don't need some asshole following me around trying to tell me what I did was right or wrong.” He swiped at his face with the towel, trying to mop up the beads of sweat beginning to crawl down his temples. He tossed the towel aside, growling in frustration. “Why is it so fucking hot in here?” he complained, tugging at the collar of his gym clothes.
Kirishima glanced around, looking confused. “It’s not,” he said, eyeing Katsuki. “You do look flushed, though,” he decided.
Katsuki cursed under his breath. “If that grape-flavored munchkin’s crap made me sick I am going to make him wish he was never born,” he decided, eyes snapping like fire. He grabbed a water bottle, holding it to his forehead, relishing the cooling sensation. Maybe he just needed a cold shower.
Kirishima looked thoughtful. “Why would Mineta’s prank affect you if it only targets omegas?”
Bakugou lowered the water bottle slowly. “It blew up in my fucking face.” Anything that exploded in your face had the potential to cause problems. Katsuki should know, he had a lot of experience with things exploding in his face.
Kirishima shrugged. “If you say so.” His eyes were calculating, sizing up Bakugou like he was beginning to see something he’d never noticed before.
Bakugou didn't like the look in his eye. “Just say whatever the fuck you're trying to say,” he told Kirishima with a scowl, wrapping his still-dripping school uniform inside the towel before cramming the bundle into his gym bag. He hated it when people talked in circles.
“Are you an omega?” Kirishima asked suddenly.
Bakugou didn't stop packing his gym bag. “Wouldn't you like to know,” he scoffed haughtily.
“Bakugou,” Kirishima pleaded, taking a step forward, “Please. Man-to-Man, I swear I won't tell anyone. Are you?”
Bakugou zipped up his bag and rose slowly, staring Kirishima dead in the eye. “Go fuck yourself.” He flung the gym bag over his shoulder, marching out of the locker room. His ears were buzzing and he felt dizzy. He was hot, hot like when he stood at the center of a maelstrom of fire. But he wasn't exploding anything… yet. There would still be time to blow up shit later. Though, he was pouring sweat, and that wasn't good. Without his costume to collect the excess sweat, he would just be dripping soggy Nitro everywhere he went. He slammed the locker room door shut with a bang, striding down the hallway, guts churning with white-hot rage. Fucking Mineta was going to pay for this. Katsuki was going to wipe the floor with that little creep.
The locker room door swung open and Kirishima hurried out after Bakugou. “Look, dude,” he said, “I’m sorry, that was shitty of me-” He laid a hand on Bakugou’s shoulder, and his touch sang through Katsuki like a soft voice carried on a cool breeze.
Bakugou gasped, finding himself melting into the other boy’s touch. He stuttered to a stop, the dizzying pounding of his head and heart slowing as his body began to sink into an almost-trance. He wanted to press into the cool, soothing touch, but instead forced himself to pull away, staggering away from Kirishima on legs limp as wet noodles. “Who said you could fuckin’ touch me?” he snapped, though Kirishima seemed to be paying him no mind.
The redhead was staring at his own hand like it had bitten him. “What was that?” he wondered aloud, before reaching out and grasping Bakugou's forearm.
Katsuki felt the same cool sensation, like ducking into an air-conditioned convenience store and chugging a cold bottle of tea in the middle of summer. His knees wobbled. He stumbled back, yanking his arm out of the other boy’s grasp, but Kirishima reached towards him again, eyes glazed over. Bakugou punched him in the face, knocking the other boy to the floor. Then, he ran. He ran past his classroom, past the nurse’s office, past the dorms. He kept running, lungs burning, arms and legs pumping, until somehow, he was home.
He scrabbled in the mailbox for the spare key and let himself in, dropping his gym bag on the floor and heading for the bathroom. He was really hot now, practically feverish, and as he began to rinse himself off outside the bathtub, he began turning the knob colder and colder, trying to chase away the heat that seemed to be burning through him like a raging wildfire. Finally, in desperation, he climbed into the bathtub and began filling it with icy water, ducking his head under the tap to try and cool his face and scalp too. Once it was full, he lay in the cold bath, fire burning him from the inside out until his mother got home and saw his gym bag lying in the middle of the floor.