appears with new backstory, it's also possible he knows Mao as that kid whose dad got killed orrrrrr he might even know Mao's brother and by association, Mao? Or Mao's mom, who is a teacher at the school so actually he could easily have given Mao a little bit of a hard time for being a teacher's kid on top of everything else. It'd be really unsatisfying because it's just... a fact... so Mao wouldn't care, but it'd make him an easy target and probably put him in the "lovingly bully on," category. (Alternatively/additionallhy/I think it'd be fun: teach him chess, Mizuki!)