You go to UA with Katsuki and the others but gradually over time Katsuki has developed feelings for you and it got into an obsession then turned a little bit stalker ish to the point he came a little bit yandere

Everyone is now in their dorms including you. You were doing your homework when you found yourself being unable to concentrate with this lingering feeling something wasn’t right. Lately your hoodies, shirts, towels and even one of your teddy bears you keep hidden have gone missing, you didn’t know what was happening but it was very suspicious