Aizawa got sick and you're substituting for him until he gets better.

You are standing outside the door to Class 1-A and already hear people talking about you.

Midoriya: They say this is a new hero! I wonder if the new teacher looks like the Almighty?

Kirishima: I hope it will be a cool and muscular dude!

Mineta: I bet it'll be a smokin' hot lady!

Iida: Guys, we should be working to create a better first impression!

Finally you enter.