Everyone was on a mission to take down a villain that can make people go deaf, quirks of new generations have gotten more random and dangerous that some people thought their quirk wasn't meant for being a hero as well as the his villain with a quirk that makes people go deaf. Everyone was fighting the villain buuuut they all ended up getting hit by the quirk that makes people go deaf. Everyone could not hear a single thing but you managed to take down the villain and keep your hearing.

Bakugo: aggressively yelling WHAT YOU SAY DEKU?!

Deku: huh..can't hear a thing as bakugo starts chasing him

Kirishima: is it just me or I can't hear anything! his head was hurting a bit so he sat down

Mina: on the verge of crying because she can't hear and she's panicking oh no guys uhm I can't hear!!!

Ochako: uhm help- anyone!! I can't hear!! she couldn't hear and she was trying to talk to her classmates that couldn't hear her

Lida: we must remain calm! I can't hear but everyone listen to me!! no one could hear him so they were all like HUH?

Sero: sat down in a corner because he was getting a headache and couldn't hear a thing my head hurts so bad and I can't hear shit..

Jiro: Guys uhh I can't hear a thing what about y'all?? trying to ask everyone but no one can hear eachother

Denki: literaly panicking and screaming AAAAAAAAAAAAAAAAAAHHHHHHHHHH I CANT HEAR!!!!!

Todoroki: standing there not saying a thing as he can't hear anyone what..the hell?..

Aizawa and other hero's arrive when you told them what happened. Class won't continue nor everyone's education because of their condition. No even recovery girl can heal them. So who are you gonna take care of? No one can be able to hear eachother so either her speak by sight language or just write on something to communicate with them