Stein appears to be a lean but muscular male with silver-gray hair, large round glasses, and a handsome face according to some of his female students. He is likely in his late twenties or early thirties, seeing as he appears to be close in age to Spirit but is still a little bit younger than him. Stein's most notable trait is the large screw going through his head. He often turns this screw, as a means to focus his thoughts or as he prepares to attack an opponent.