When Izuku Midoriya turned four years old, he knew two things: He wanted to be a Hero like All Might more than anything in the world and that he was destined to be mated to Katsuki Bakugou.
At the age of nineteen and freshly graduated from U.A., his first wish was well on track. While his Quirkless childhood had done its best to condemn Izuku to a civilian lifestyle, thanks to All Might himself and the wondrous power of One for All, there was no doubt in Izuku’s mind that he would fulfill the legacy placed upon his head and carry on the name of the Symbol of Peace.
His second goal of courting Kacchan was a work in progress, but Izuku had hope. He was still young and there was plenty of time yet to work on relationships while he started his Hero Career proper.
Truth be told, only Kacchan could make the simple act of mating more difficult than acquiring a Quirk.
But that was fine, really. A part of Izuku preferred it that way because stubbornness was just something Kacchan excelled at and there was a thrill that came with the pursuit that cried out to the more primal instincts of his inner being. And despite what Uraraka and Iida would tell you, Izuku knew how to be patient when things mattered.
Enough so that when Izuku had presented as an Alpha—not only a year earlier than his peers, but also to the surprise of his two Beta parents—he had fully resigned himself to a life of perversion if need be.
Kacchan had had “Alpha” written all over him as a child with his dominant personality, sharp canines, and fearsome Quirk. Aggression suited him and he was the picture perfect image of his Alpha mother.
Even knowing that Kacchan would likely present as the most aggressive and dominant of the three classes, Izuku found his interest in the other did not fade. If anything, his crush on Kacchan had remained as strong as ever, only increasing as he grew to admire the other’s strong presence and dedication to victory. Even Kacchan’s indifference and occasional violence aimed at Izuku’s “uselessness” as they grew up through elementary and middle school did nothing to deter his desire to be mated with Kacchan when they came of age.
Izuku couldn’t help himself. It was like fate itself had ripped out his heart and handed it to Kacchan to do with what he pleased.
As more and more of their peers presented their secondary classifications, Izuku had grown anxious of how things would work if Kacchan also presented as an Alpha when his own affections had refused to waver. No one caught his attention like Kacchan did whenever he bragged or smiled. No one smelled as good. No one else even blipped Izuku’s radar. Being mated to anyone else just didn’t register as an option.
Ever difficult, Kacchan did Izuku’s wild imagination no favors by being a late bloomer. Even by the end of their third year of middle school, he still hadn’t presented, even though it seemed “Alpha” was the inevitable choice.
So Izuku had researched.
Alpha-Alpha pairings were ultimately considered a perversion: A failure of biology that refused to take advantage of the Alpha’s fertile nature to pass on their genes, as well as an abandonment of the “natural course” that made them lust for and satisfy the needs of an Omega spouse.
They still happened, however, so young Izuku had held out hope he might be able to one day convince or seduce Kacchan into a life of debauchery.
(Or at least be enough of an influence that Kacchan might consider a second spouse in addition to whatever Omega might catch his fancy. There were always other options, even if Izuku would have to grit his teeth through them.)
Thankfully, it never became a problem.
During their second year at U.A., his slightly-matured Kacchan had presented as a Beta two weeks after he had been bedridden with the flu. His mother believed that the severe illness had finally kickstarted Kacchan’s hormones into gear from their resting state. Izuku wasn’t quite sure how it really worked, but Kacchan walked into class finally sporting his own unique scent all the same, albeit dulled due to his Beta class. Kacchan had been overall disappointed he wasn’t an Alpha, but sometimes life worked out that way.
Izuku, on the other hand, couldn’t remember the last time he had been so relieved.
Alpha-Beta pairings were looked down upon, but not uncommon—case in point, Kacchan’s father was a Beta. And best of all, Beta were capable of childbirth. True, they would only have one or two children over the course of their lifetime compared to the full, multiple litters Omega could produce, but Izuku would be happy with one child if it was with Kacchan.
But the gratefulness of knowing he wouldn’t be a total social outcast was nothing compared to the relief of knowing Kacchan wasn’t an Omega.
A secret, ugly part of Izuku fantasized about it once in a while during those long years while he had waited for Kacchan to present. There was a reason that the Alpha-Omega match was expected and why entire Matchmaking Houses were dedicated to it. They fit together the way biology had designed; two halves meant to complete each other.
Izuku would not deny the thought of Kacchan on his back, begging Izuku to take care of him, had kept his fifteen year old self up at night—multiple nights—until the reality of what that would have meant set in. The terror that Izuku might lose Kacchan forever if he had presented as anything other than an Beta or Alpha had kept him up at night after that in a far more unpleasant fashion.
No matter how nice of a daydream Kacchan being an Omega would be, it wasn’t worth the risk of some other Alpha getting their hands on Kacchan first. The thought filled him with a rage he could only blame on natural forces beyond his control.
Being a Beta was the best outcome without question.
And not just because Izuku wouldn’t have to suffer the title of “pervert” for the rest of his life.
Kacchan’s Beta class meant he wasn’t particularly desirable from a biological front for the Alpha looking to have large families and his strong personality kept the rest of them away. Kacchan wasn’t scared to butt heads with other Alpha, posturing and yelling and growling just as loudly as any of them might. He may have been a Beta, but as far as other Alpha were concerned, it’d be like dating one of their own—a fact Izuku had learned long ago most weren’t even willing to consider.
Other Beta who showed interest were easy enough to discourage to the point they weren’t even a concern. No Beta would dare challenge Izuku when he’d made his own interest in courting Bakugou well known.
Kacchan could stay single for now all he liked. Eventually, he’d feel that same natural tug to mate that the rest of the population experienced and when that day came, Izuku would be right there waiting for him.