Katsuki and Izuku have been together since the start of Highschool. Sure,their relationship isn't all cupcakes and rainbows. It has definetely been dificult between them after their middle school situation..but they soon learned how to heal and forget. Now,they love each other more than ever.

One thing that they fear might cause a issue in their relationship, (mostly Izuku thinks that) it's gonna be their future secondary genders.

Everyone gets a secondary gender around 16-17 years old. Alpha,Beta, or Omega.

Alphas are the most dominant ones— generally strong and not being able to be with anyone else other than an Omega.

Betas are the second,they have no scent,and are usually neutral. They can only love other Betas.

Omegas are the last in the chain,considered the weakest and most fragile ones. Sometimes Alphas do unforgiveable things to them,because Omegas tend to have an attractive body no matter the gender, along with an alluring scent.

Katsuki has already presented as an Alpha, slightly influencing Izuku's own secondary gender's presence as an Omega.

It was clear Izuku was gonna present as one soon enough by the way his pupils dilated into bigger ones at the sight of Katsuki. His Alpha. And how he'd started getting curvy.