Chapter Text
Eijiro was a Beta who was raised by two Beta women. He wasn’t well-versed in the Alpha Omega dynamics and even in school, try as he might to join in on the pack scenting and bonding, he always seemed to be the odd man out. Even up into middle school, Eijiro struggled with how he fit into the dynamics of his world. Betas were not terribly common—as generations went on, it seemed fewer and fewer of them were being born.
He assumed he would follow in his mothers’ footsteps and find a Beta as well. That was until Eijiro Kirishima found himself the front horse of Katsuki Bakugo, UA’s most feral Omega, at the first-year sports festival.
After that, he was completely smitten with the man. Katsuki never second-guessed a thing. He knew what he wanted, he knew his worth, and he knew his dynamic. He was proud of anything and everything he did; he was incredible.
He taught Eijiro a lot during their first year of high school and halfway through the second year they began dating. It happened slowly; Eijiro wasn’t even aware of it. Through soft touches and quiet words that were swallowed under dark covers. Nightmares whisked away by calloused hands through soft hair. Their nightly ritual of getting lost in each other's arms and sheets was an unspoken routine, and he had no idea Katsuki thought of that time as anything more than a platonic comfort. God knew Eijiro clung to those quiet hours he spent tucked into the blond’s side, wishing Katsuki wanted him as desperately as he wanted the Omega.
Their relationship never had a name until a Beta from general studies asked Eijiro out and Katsuki nearly choked out the room in his anger. Burnt plastic curdling in the air, his teeth bared in a near-feral display. The poor girl left in such a state of shock and Eijiro was right along with her, completely stunned by the reaction. He had no intention of accepting the girl’s offer but Katsuki had jumped in before he got a word in.
It wasn’t until Katsuki had dragged him out of study hall right after the interaction, cornered him under a stairwell, and reamed him for not turning her down sooner, that the words left the blond’s mouth.
“You’re my mate, shitty hair,” Katsuki snarled.
It was a bold statement. People would go steady in high school, test the waters—the M-word was heavy, loaded with implications of things people their age could never be sure of. But Katsuki Bakugo was sure of everything.
They kept it quiet at first. Neither of them wore a mark, so it wasn’t anything official, but their touching became more intentional. Their bed-sharing was filled with more skin and less space. And Eijiro was learning quickly about dynamics, and how both of them worked together.
Katsuki relied heavily on his scent when it came to relaying his feelings. He would stink up a room at a moment’s notice if he had to; his emotions were loud and people would hear them. The only issue was Eijiro’s nose wasn’t as keen as the others, only ever picking up the slightest wafts of over-brewed coffee, but it was a smell he would chase to the ends of the earth. Although it could be frustrating, being unable to pick up the subtle hints his mate scented, especially because his lack of instincts didn't allow him to fill the gaps by reading the Omega's body language. Sadly, facial expressions were no help either—Katsuki always wore a resting bitch face. They both needed work on reading each other, like they each had to learn a new language to truly communicate. Katsuki found himself becoming more vocal and Eijiro picked up on the subtle changes in his tones, purrs, trills, and yelps.
Slowly, both of them learned each other’s weak points and worked on them. Eijiro hadn’t realized just how attuned he had become to Katsuki until one day he was rummaging through the kitchen for snacks. It was nearing the end of their second year and they were all stressed and tired as the course load grew, and a small scuffle could be heard from the lounge area.
Looking back, it was nothing but Katsuki getting annoyed with Izuku. But around the end of first year, Izuku had stopped taking the blond’s shit and gave back everything Katsuki dished out. So, it shouldn’t have been a surprise when Katsuki let out a small yelp after Izuku pinned him under his knee. That was what the rational part of Eijiro’s brain would say, now that he had time to look back at it.
But at that moment, the second he heard Katsuki yelp, he stormed into the adjoining room. The biggest snarl he could manage was stretched across his face and his, thankfully, sharp teeth bared down at Izuku, an Alpha. His vocal cords were not quite made to create the low, skin-prickling rumble an Alpha was known for, but he did his best, scratching his throat in the process.
Izuku quickly hopped off Katsuki, more surprised at Eijiro’s outburst than scared, his wide green eyes snapping back and forth between the two of them. Eijiro dropped to his knees to look over Katsuki. He was sprawled out on his back but looked fine; the yelp was involuntary and absolutely unintentional.
“M’fine; fuck off,” he mumbled, but Eijiro could hear it, the quietest purr, nearly inaudible rumbling from his mate’s chest. He was proud of him. Warmth bloomed in Eijiro’s chest and for the first time, he felt like he was beginning to stand on equal ground with Katsuki.
After that incident, it was very clear where their relationship stood. It wasn’t like they were hiding it before, they just kept their displays of affection to themselves. But since everyone knew, they slowly started becoming more open around their friends.
Graduation and moving out happened in a blur, but they did it together. They ended up at different agencies in the same city and life seemed almost perfect. They exchanged bonding marks during Katsuki’s first heat out of UA. Eijiro had never been prouder in his life. He didn’t have Alpha fangs but he had a mouth full of razor-sharp teeth that left one of the manliest markings he had ever seen.
Eijiro had caught Katsuki on many occasions looking at it in the mirror, a small smile on his face. Eijiro would come up behind him and place a kiss on the fresh mark, compliment how nice it looked, but his mate would roll his eyes and shrug him off, that small upturn of his lips never leaving.
The media went into a frenzy after they returned from that heat. Pro Hero DynaMight Has A Mating Mark.
No one seemed to notice Red Riot had its matching counterpart. For all the media knew or wanted to know, they were the best of friends and roommates.
Eijiro was used to Betas being treated as such. In a world run by Alphas and Omegas, he was the lowest status. People assumed he would mate with another Beta; that was how it normally went. Who would have thought a loud, brash, overachiever like Katsuki would settle for a Beta?
“I didn’t settle for anything, you fucker!” Katsuki grabbed the mic and yelled before blowing it up in his hand and flipping off the camera. The interview followed a routine takedown of a low-level villain. It had taken them months of correcting people in interviews for anyone to finally begin seeing them as mates, and even years later they would have to correct people.
But it almost seemed worse once the media finally got on board, like they had to know why Katsuki picked Eijiro.
Eijiro knew how the world saw him—he was large for a Beta and a great hero, but he was lacking in the public’s eye. A watered-down version of both secondary genders.
Katsuki would never say such a thing, and he would come home fuming when interviews like that happened, or if the internet was feeling especially vicious. Their relationship was always under scrutiny and Eijiro couldn’t help but feel responsible.
It seemed like Eijiro’s nose was broken half the time, but one scent he could pick out anywhere was Katsuki’s heat. It was strong and sweet on his tongue, like sugar melting in his mouth, thick syrup down his throat warming his body as his mate’s pheromones surrounded him in thick perfume. It was the one time Eijiro felt like he was actually sensing what all his friends and coworkers did. His nose was so attuned to the smell of Katsuki’s heat, and he knew exactly what to do once the delicious scent tickled his nose.
It was a learning curve; he remembered the first heat they shared. Eijiro was painfully unprepared for it. By day two he was nearly useless and Katsuki was a mess . Since then, he had learned exactly how to approach it and with a plethora of heat aids, they managed it rather successfully.
Katsuki’s back arched as Eijiro plunged the knotted dildo completely inside him, slick seeping out around the thick toy. The blond came with a loud cry and spilled thin ropes across his stomach. Katsuki’s cock twitched with the release, a few beads dripping out and across his abs.
Eijiro loved having sex with Katsuki and he had a rather high sex drive, especially for a Beta, but he couldn’t keep up with him in heat all the time. They gathered quite an impressive collection of dildos. He would knot his Omega two more times before he would be able to fuck him with his own cock again. His refractory period got longer and longer as the days went on. Try as he might, Katsuki's pheromones didn’t trigger a marathon sexcapade in him. While the scent made his mouth water, it was more of a Pavlovian effect rather than an instinctual one.
“Alpha,” Katsuki whined, as he rolled back onto the dildo, his hole already clenching down and seeking more. Eijiro knew Katsuki’s body worked futilely to milk the silicone knot for cum.
“I know, baby.” Eijiro ran his fingers over Katsuki’s marbled thigh, sticky with sweat and slick. “I’ll take care of you.” Eijiro leaned down to wrap his lips over Katsuki’s soft cock, swirling his tongue around his cum-soaked tip. Katsuki mewled and he bucked up into Eijiro’s mouth. Slowly, he could feel his mate’s cock begin to swell on his tongue.
The redhead began moving the dildo slightly, not pulling the knot free of Katsuki’s hole, just rolling his wrist enough to tug on his rim with the thick knot, bumping it against his prostate as he sucked the cum clean off his cock.
“Yes, yes, Alpha !” Katsuki’s fingers curled into Eijiro’s hair. Rocking his hips between his mouth and the dildo, going dizzy from the stimulation.
Katsuki’s cock had fully swelled in Eijiro’s mouth and he began taking his length deeper, letting it bump the back of his throat. Pre slipped across Eijiros’s tongue as he pulled back enough to swirl his tongue over Katsuki’s bright red tip, the veins down his shaft turning purple as he thrashed. Eijiro saw Katsuki’s balls draw tight, his feet pressing into the redhead’s back, toes digging into sweat-slick skin.
Eijiro moved his mouth in tandem with the dildo and his Omega began falling apart under him; Eijiro had lost track of how many times Katsuki had spilled out onto his tongue. The Beta drank it down, proud that he satiated his mate’s needs.
Eijiro sat back up and looked down at Katsuki—his muscles glistened with sweat as his thighs twitched with release. He was utterly exhausted, skin flushed from heat and chest rising and falling at a quicker pace. It was day five and they were both barely able to keep their eyes open between knottings.
“How are you feeling, Katsu?” Eijiro traced his hand down his mate's calf, soft strokes over pliant muscles, melting him into a puddle of satisfaction.
“Good. Tired,” the blond mumbled as he let his eyes close. Eijiro crawled up the bed and pulled his mate towards him, tucking him under his chin and surrounding him with large arms. Eijiro left the knot in him knowing his body would let him sleep longer if it was still there.
“Sleep, Omega,” he spoke softly into blond tufts of hair.
They must have stayed like that for at least two hours, until Eijiro was woken up by the strong frame of his mate straddling his hips. His fists worked Eijiro’s cock to full stiffness in his sleep and just before Katsuki dropped his hips and fully seated himself on his dick, the Beta’s eyes snapped open.
Katsuki’s body seemed to be quivering in anticipation as he fumbled with Eijiro’s cock, not wanting to waste a single minute. But once he managed to press the tip against his wet entrance, he dropped his weight, sheathing himself with a satisfying slap of skin.
“Oh, Alpha, yes.” Katsuki preened as he rocked his hips. “Just like that,” he moaned, quickly picking up speed, his walls hot with cum and slick, milking Eijiro before they even truly began.
“Katsu!” Eijiro was breathless before he even fully woke up. His hips snapping up on instinct, wanting to fuck into him. Eijiro’s hands found themselves on his mate’s hips, sliding his fingers up to wrap around his small waist. They slipped over hard-earned abs, one hand jutting up to knead Katsuki’s tit. Everything about him was so fucking perfect; Eijiro actively fought back his orgasm while his mate rode him like his life depended on it.
“Yeah, yeah, Alpha; come on, fuck me.” Katsuki’s head tipped back and his chest pressed forward. His pecks bounced every time he dropped his weight onto Eijiro’s cock and the Beta was mesmerized.
Even half-delirious from exhaustion and barely having had enough time to eat or drink, Eijiro was still so in love with his mate moved. He wouldn’t trade this time for anything. Katsuki’s thighs rippled as he rocked his eager hips, the muscles in his arms flexing and relaxing each time Eijiro’s cock brushed against his prostate, nails scraping at tanned skin for purchase, dragging red streaks across his well-defined chest.
He began meeting the Omega’s thrusts halfway, slapping their skin together, biting his nails into tender flesh, and fucking his mate hard and deep until the blonde was teetering on the edge of release.
“Come on, baby, cum on your Alpha’s knot.” Katsuki’s hand jumped to his bobbing cock, a thin line of pre connecting it to Eijiro’s stomach every time the Omega dropped, causing his dick to slap against the Beta’s firm abs. “Yeah, that’s it; I want to be covered in it.”
Katsuki let a string of whines leave his lips. He was so far gone, Eijiro could feel his walls milking him, clenching down, and Katsuki let out a long whine as his body trembled in release, just before cum splattered across Eijiro’s chest and face. Once Katsuki came, the Beta stilled his hips, not wanting to finish just yet, knowing the Omega would be ready in a few minutes for another round. Katsuki hated when Eijiro stopped his post-orgasm rocking, but they were both so tired.
“Good boy, Katsuki.” Eijiro released his grip and trailed his hands all over his mate's torso; it heaved with breath and he looked absolutely exhausted. “Come here.” Eijiro pulled him down towards him and Katsuki fell into a kiss.
It started off slow; they were exhausted, spent from days of sex. But these moments were just as important as fucking during heat. His Omega being seen, felt, loved, cared for. Those instincts came naturally to Eijiro—loving Katsuki always did.
It wasn’t something he had to learn, and if anything, he had taught his mate some in this department.
The long, slow drag of tired lips, the slip of clumsy tongues and teeth, the smell of arousal in the air turned to a content hum, like coffee and sweet cream at Eijiro’s nose. It was so strong and Eijiro basked in the moments he could drink in his mate's scent so clearly.
His Omega melted, strong muscles became jelly in his arms, and they took as much from the moment as they could. Eijiro could spend the rest of his life in post-orgasmic bliss with his mate. Katsuki became so soft, his ridged edges filed down to smooth corners for Eijiro to press into. It was something no other person had the privilege to experience.
But it wouldn’t last, because Katsuki’s scent became sugary sweet moments later, any ounce of coffee was overcome with another wave of arousal.
Before Katsuki could even ask, Eijiro flipped them over, cock still buried inside him. Caging his mate in on either side he started a slow, deep roll of his hips. But it didn’t last long; Katsuki’s moans turned to whimpers and he wanted more, he needed release. There wasn’t much foreplay in heat sex—it was done for one reason. To breed.
Eijiro wasn’t sure if it was an issue or a blessing. He was sure it could be both at different times of their lives, but a male Omega, male Beta relationship was usually met with fertility issues.
It had happened on two separate occasions in their lives. Forgetting to take birth control and still ending up without a pup. Not that they were trying, still only a few years out of high school; they thought they had time. But it was another thing to add to Eijiro’s list of shortcomings.
Katsuki arched his back and gripped Eijiro’s biceps, and he managed to land his angle just right.
“I’ve got you, baby,” Eijiro cooed. He took one of Katsuki’s legs and hooked it over his shoulder, allowing him to thrust deeper, fully burying his cock into the blond.
The change in angle had Katsuki gasping, babbling a string of words that usually preceded his orgasm. Moments later, Eijiro watched as Katsuki’s cock, red and engorged with blood, twitched. His body trembled in his release and he seemed to let out a sob like it was painful.
“Yes, Alpha!” His voice shook as his dick continued to pulse, but no cum came out. He was passing his point; they both barely had anything left. So his cock twitched in a pathetic, dry, borderline painful orgasm as tears beaded in the Omega’s eyes.
Eijiro had to make this one count; he wasn’t sure how much more either of them could take. A few more thrusts and Eijiro was cumming deep into Katsuki’s tight heat. He didn’t have the privilege to enjoy the way his cock pulsed inside his mate’s tight walls. Pulling out quickly he grabbed for the knotted dildo and slid it right in, satiating his mate’s need for cum and a knot so that Katsuki quickly sank into the bedspread with a purr.
The Omega fell asleep quickly after that, his body tucked into Eijiro’s as he stroked soft circles into his back, fighting back the slight feeling of inadequacy as the knotted dildo eased his mate into a state of rest.
Even with the slow decline of Betas, there were still others out there like them. It wasn’t an impossible match-up by a long shot, but it did come with some issues, heat being the main one. While Eijiro was always ready to serve and take care of Katsuki in any way possible during this time, it took a lot out of both of them.
Eijriou's body wasn’t built for Katsuki—a thought he felt himself stomping out multiple times a week. He didn’t release hormones and pheromones like an Alpha did; while there was no way he could trigger a heat in Katsuki, there was also no way to stifle it.
Alphas and Omegas were meant to be mates. Their cycles, instincts, and bodily makeup were all made with the other in mind. An Alpha’s pheromones shortened and soothed an Omega's heat, and vice versa.
Eijiro couldn’t do that. He couldn’t satisfy the core need of Katsuki’s Omega, and by the seventh day—because that was how long Omegas go into heat when not accompanied by an Alpha—they were both exhausted and sore.
If Eijiro was an Alpha, he could have Katsuki’s heats taken care of in three days tops. They could both be back at work with minimal time missed. Katsuki would never admit that, and the one time Eijiro even mentioned buying Alpha pheromones, he nearly lost his head for it.
“Why would I want some strange fucking Alpha to stink up my room? I want you ; I like how you smell.”
“I don’t even have a scent, Kats.” Eijiro nearly whined; he wanted to make life easier for his mate. Why was he fighting him?
“Yes, you do, idiot. You smell like…” He paused and his voice got quieter. “You smell like clay and earth, after a huge thunderstorm.”
“I smell like mud,” Eijiro shot back.
“You smell like my mate ,” Katsuki finished.
He quickly shut his mouth after that. Eijiro would never allow Katsuki to criticize his Omega scent, freshly brewed coffee, a mix of bitter and a dash of sweet, just like his personality. Just because he wasn’t as attuned to the world of scents didn’t mean they weren’t there.
“So, no pherom—”
“Absolutely not, hair for brains!” Katsuki snapped, and the conversation was dropped.
But his search for a solution didn’t stop there, and as Katsuki slept heavily in his arms Eijiro began coming up with his next plan.
Eijiro wasn’t sure how he found himself pursuing the agency’s quirk database. He was sure it was against company policy to do what he was doing, but he had to try. A few different wordings on presentation and dynamics, and in less than fifteen minutes he had struck gold.
Azumi Masuda, quirk: Pheromones. She had the ability to change your presentation for up to seventy-two hours. Eijiro nearly fell out of his chair when he found her, and she lived only a two-hour train ride away. Katsuki’s heat was a month away; he could get in contact with this woman and see if she could do anything for him. It would be a perfect surprise.
Ei quickly jotted down all of her info and tried to push down the feeling of guilt that sat in his stomach over how he obtained the information. Stuffing the paper into the side of his bag, he closed out of his tabs and stood up to start his patrol, trying to control the extra pep in his step as he wandered out of his office.
It was a nerve-wracking week; Eijiro was jumpy and a little twitchy. Katsuki had chewed him out on a few occasions over his actions. His pre-heat nerves were not helping the situation and Eijiro tried to stay on his mate’s good side and act as normal as possible. But it was difficult; he was so unbelievably excited and not being able to share that feeling with Katsuki was hard. He was also a little nervous—Eijiro hadn’t known anything but being a Beta, and neither did his mothers. Katsuki was the biggest influence outside his family he had, and even after years together he still found himself confused. While he knew more now than he used to, some stuff just didn’t click in his mind. And he worried that even with this quirk, he would still be just as confused.
“The fuck crawled up your ass?” Katsuki bit out as Ei nearly leapt from bed; Katsuki was entering the final few hours of pre-heat and he would probably be in the throes of it by tonight. Even Ei’s dull nose could pick up on all the new scents filling their home. It made his mouth water, not that pheromones had much of an effect on him in a biological way, but more of a Pavlov’s dog type of way. Ei was trained to respond to Katsuki.
“Nothing, I just have a few errands to run before tonight.” Eijiro tried to hold his voice steady, he was a terrible liar—it just wasn’t manly. But he had to; this was going to be the surprise of all surprises and he was finally going to satisfy his mate.
“No,” Katsuki said, harsh and demanding. Eijiro knew that would be his reaction; he knew he was not leaving this house without a small battle. Because even though all the Omega stereotypes depicted them as soft and sweet and darling things, Katsuki was hellfire and grit, and Ei loved every single part of it. But it led to conversations like this.
“Kats—”
“You are getting back into this nest…” Ei watched as the blond’s face curled into a frown, his brow creasing and lips thinning into an expression that really could have an Alpha rolling onto his back. But he had a goal; he needed to leave…now.
“I promise, I will be back,” Ei assured. “You won’t even have time to miss me!” He leaned back over the bed and placed a kiss on Katsuki’s grimace, and he could see something flash in his eyes, like the smallest waver of his steadfast will.
He couldn’t help but feel bad leaving; this was an important time for Katsuki, a sensitive one. It was something he took incredibly seriously—not that he didn’t take everything in life incredibly seriously. But it was necessary, and in a few hours, Ei would be back home, new and improved.
He could do it, because in reality, how different could an Alpha really be?