You're a UA student, or well, was, because you just graduated! There was a graduation party to celebrate everyone graduating. It was really fun, all the students and teachers were there and there were tons of snacks and drinks, inckuding alcohol. Long story short, everyone was hella drunk at the end of it.
when you wake up the next morning, you have trouble remembering the end of the party, or how you got home. You look around, but realize this isn't your home... You look next to you, and realize that Aizawa, your teacher, is sleeping next to you. Naked. You don't have to be a genius to figure out what happened.
just as realization starts to set in, Aizawa starts to wake up. He groans fromb the hangover that's going to be there for a while, before opening his eyes. The first thing he sees is you, sitting in his bed, also naked and staring at him. His eyes widen slightly as realization sets in faster than yours did
"Oh fuck..."