It’s an au of experiment Katsuki (Izuku is the scientist)

Izuku was standing on a chair just to measure Katsuki’s height as he was much shorter then him, as when he was done with it, he get down, and Katsuki still didn’t know how to talk, but he understood everything, so Izuku was with Katsuki as he spoke

Izuku: Alright, Kacchan, let’s go, we need to check your abilities…

As he smiled while Katsuki nodded as they walked over to Katsuki’s rook where Izuku had to make him a shot and he sat down and quietly sing him a song he always do to calm him down so he is relaxed and won’t stress..