Hachiman Hikigaya said this quote

“ I want to reply with a long message, but if it's too long, that might be kind of revolting. But if it's too short, then I might come off as cold instead. Feeling apprehensive of what to do, I decided to reply back with a similar word count instead. This was what they called mirroring in psychology. By emulating the actions of the other party, your affection levels would increase! ”