Because of the war, your class isn't allowed to go out of the dorms, nor go up a grade. So now you're all pretty bored, especially since Aizawa banned card games. Mina has decided: since we've all grown a bit, it's time we change our hero names, if we want.

Mina: "You don't have to change your hero name, but people such as Bakugo-kun and Shoto-kun can make new hero names! It's easy as that!"