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

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