So

What I got from his reaction and his past is that he uses the mask to cover his mouth, not to cover his mole. Yeah the mole is a part of it but not as much as him saying harsh words. It's like he has no filter so the mask is the filter. The only one besides family sayama seems to let the filter run loose with is saikawa. Idk what triggered him to be so harsh, or why he cant hold himself back from saying certain things, maybe its a condition similar to tourettes or trauma from even before that girl but I hope its expanded upon. Cause what I'm getting at is that the mask isnt to hide his face cause he things its ugly or weird but to just not stand out and cause conversations, like people pointing out his mole, where he may have to speak and then show he has no filter and say things he doesn't mean. Kinda like a tsundere but to the extreme.