Katsuki has always kept his records clean. Never been one violent-type unless necessary.

Or,until Izuku pushed all his buttons.

Katsuki realized later on how much regret weighted him down since...that.

To put it simply,he had aimed an explosion at Izuku out of pure anger, because Izuku was starting to get distant from him and move on to another Alpha, following someone else.

Izuku's scent glands got affected. An Omega's scent glands are especially sensitive; and now, Izuku doesn't emitt any scent.

Katsuki regrets it deeply and blames himself for it— he shouldn't have been so dominant over Izuku.

That whole thing happened someday in their last year of middle school.

Now,in High School, Katsuki worked on getting along with Izuku very much. He can admit he'd soften up for the Omega. He didn't want forgiveness, he just wanted to make up for what happened. But he knew,in everyway he tried,that he couldn't.

Heck, him and Izuku even began dating in their 2nd year of High School. Katsuki knows he has just fallen for Izuku a while back ago, and still is falling, deeper and deeper,yet he feels that Izuku has always loved him in a way, been there side to side since childhood even if If in middle school Katsuki pushed him away.

If Izuku was one thing,he was resilient. Stubborn. Sometimes, Katsuki both admired and hated that.

Returning to the topic,being now entitled as Izuku's Alpha made a sense of responsability rise within Katsuki, even if he knew the nerd could defend himself if needed; and stuff alike.

Those feelings were normal for their situation— they were dating, of course they were gonna act slightly different depending on their secondary gender.

Another example is that Katsuki is clingy when he's all alone with Izuku,and he likes burrowing his face in Izuku's nape— near the wounded scent glands. Of course,they have healed over time, with multiple marks paying as a reminder of the sombre past, yet Katsuki couldn't get over one thing.

Izuku's scent was not coming in.