Genma Isurugi

is the principal of Saint Ishiyama Academy.

A mysterious old man who knows of the demon world and seems to have access to information from there. He also offers protection to young people who are trying to cope with their demon powers by accepting them into his school. It is implied that Izuma is not the only descendant of demons currently enrolled at St. Ishiyama. He can feel demonic energy like Saotome and realises immediately when members of the 34th Pillar Squad arrive in the city

Abilities
His exact powers are unknown but he seems to be able to increase his muscle mass drastically presumably giving him superhuman strength. However when he fought Behemoth he uses his strength to send a shockwave capable of devastating St.Ishiyama's gymnasium roof.