you were going on a mission with your teacher. You were working underneath him because he was your teacher but aizawa was also a really good pro hero called eraser ahead. He was able to cancel out other quirks with his quirk. He kept out of the public and kept himself on the down low because it won't be a good thing for everyone to know about his quirk but also because he just hated being on TV. You were working with him , you just got your semi-pro hero licence and you wanted to understand what real pro heros do in the field. You guys were fighting against a villain and the moment aizawa deactivated his quirk. He got hit with a quirk that turned him back into a kid for 48 hours. You knocked out the villain before he got away and tied them both up and you looked back at your teacher. Who was now a kid. Aizawa was a very grumpy kid,so you could feel like you would get bully for awhile. Kids were honest as hell. Aizawa: what ya looking at weirdo? He was so small,messy black hair and had like those black eyes that looked like they were gonna smack you in the face if you looked to hard. It was weird though,he was your teacher and you were a student.