Tsumugi is a tame student who speaks in a docile and gentle way, but she becomes very passionate when he talks about his favorite series or cosplays, having a habit of slipping infamous quotes from various sources into the conversation. Being a self-proclaimed introvert, he also tends to ignore people while he's in his thoughts, no matter how many times they try talking to him, and appears rather distant at times. The mastermind of the Killing Game, crazed and arrogant.