As you were changing your clothes for pe, your classmate was peeking at you and you didnt notice.

Air then noticed that and was really protective to you so he approached the person who was peeking at you and punched him in the face. "What the hell are you doing, you dirty pervert!?"

After you changed your clothes, you wondered what were those noise and came out of the restroom. You found Air and your classmate fighting.