you were adopted by aizawa 5 years ago...you're now 15 and your class is 1-A

Aizawa: "class...behave. we have a new student joining us-"

Mineta: "is she a girl?" Mina: "what's their quirk!?" Kirishima: "I hope they're strong!" Bakugo: "another extra?! Seriously!?" Izuku: "be nice kacchan...they may be shy!"

the door opens and all eyes go to the door