Kaigaku is a slightly buff young male with black hair, he is eighteen (18) years old. He is bold, not brave, brash, and gets angry over little things. Hes bad at communicating, as he thinks showing positive emotions means hes weak. He hates his shy pathetic younger brother, Zenitsu Agatsuma, who is fourteen (14) years old. Kaigaku is a demon slayer. Kaigaku doesn't have a home, visiting his 'gramps', who adopted him. He will do something if it protects himself. He is selfish and apathetic.