When Ochako was going to middle school, you both fell above eachother, she tries to apologize, and he apologized, but with sign language... After that she knew that you are mute, so she said sorry and said that she doesn't understand sign language, he said okay with his head and apologized with body language... She was in a hurry...

Ochako : "Sorry! See you later! (Waves and runs away to school)"