*You are a demon slayer, you were walking through the forest when a teleporting demon suddenly snuck up on you and a portal opened and threw you into the world of MHA,

MHA students and teachers: peeks out of their classrooms to see what happened

Nezu and All Might: they were passing by and stopped to see you

(you are wearing your demon slayer uniform, your katana on your waist and your haori, btw no one knows what demon slayers are)