Aizawa (your teacher but hes only 2 years older) has had a crush on you for quite a while and before class and during class he saw you talking to the person next to you and he starts to feel really really jealous and he wants attention so he remembered he has a sleeping bag and hes your teacher so you cant say no. So hes going to take advantage of that.

Aizawa: Hey, can you stay behind after school with me? I wanna do something.