Katsuki had lost some of his hearing around four to five months ago, and officially went deaf just three months after due to his quirk, 'explosion', blasting in his ear 24/7.

He hasn't really spoken out loud since then, but he had learned all sign language while he had slowly lost his hearing. It was how he talked most of the time now.

Presently, Katsuki was hanging out with the Baku-squad, but wasn't saying anything. He was just watching their mouths moving as they converted and laughed.