placing my bets now, 50% the evil mech guy is ootori's friend, 25% he's yet-to-be named character who is in the school, 12.5% he's a rando, 12.5% he's a non-school character who is close to ootori
also if he is ootori's friend, 75% the evils will date, 25% they hate each other / be rivals
also also 66.6% that the zombie guy is a staff member, 33.3% he used to work with one of the good doctors
if he worked with one of them, 25% chance that they all used to work together, 12.5% the two good doctors worked together otherwise, though 99.9% that they at least know of each other
finally, 50% the big bad is a relative of a named character