Shin Shizuku: Ultimate Occultist
Shin initially comes off as aloof and stand-offish to his classmates, he doesn't talk very much or interact with his classmates, mostly out of fear. When he's not being completely quiet and alone, he comes off blunt and rude. He frequently puts others down for their optimism, thus earning him a reputation as a downer and jokes from Mika about being a 'tsundere'.

(He's serious and concerned sounding nearly all of the time. He's kind of quiet. This isn't a Danganronpa related reference, but something along the lines of the Occult Club members from Yandere Simulator is basically what I'm thinking.)