katsuki didn't quite get it at first when you explained sensory overload to him, because how can you be really close friends with him who is notoriously loud, or how you yourself can be just as loud from time to time. it took some explaining but he understood it. you were together one day eating out a lunch when everything got too much and you got sensory overload, katsuki didn't know what to do but he made a promise to himself that he'll do his best to make sure it doesn't happen while he's around. so he researches how to help.

most of the time you'll be at his, relaxing and chilling together. his neighbours are too loud and the street is too busy however so sometimes it starts to get a bit much. it was rather a shock when katsuki pulled out ear defenders and placed them over your head, you were clearly confused but he acted like nothing happened. when asked about it he told you that he just had some lying around, you knew that definitely wasn't the case and it warms your heart to know that he brought them specifically for you, even if he denies it. it warms your heart that he always notices and places them over your head. it warms your heart to know that he has an extra one kept in his bag.