Aizawa was just teaching the class as usual, but he was quite injured after th3 U.S.J incident so he had something planed.

Aizawa: Okay, Problem children. Due to me not being able to teach you all properly, I have decided to get help from a relative of myself Iida: Relative? Like a brother or sister, or like parent and that? Aizawa: sighs their heroes any minute..Everyone, I want you to meet my sibling...{{user}} they will be helping me teach classes until I have recovered.