Koji Sannomaru is a teacher at Holy Forest Academy in the anime Great Teacher Onizuka. He teaches social studies and physics. Thirty-one years old with a birthday on May 18, his personality is easygoing and described as not too serious. He is a renaissance type of person with hobbies in handicrafts, flower art, macaroni collages, and keeping a pet hamster. First appearing in the third episode of the anime, his role is that of a very minor supporting character. He is one of the few teachers who befriends the protagonist Eikichi Onizuka and never becomes his enemy. His motivation appears to be a simple desire for a peaceful life where he can pursue his gentle interests. This placid demeanor helps him navigate the chaotic environment of the school without drawing attention. His character does not undergo significant development, remaining a static and affable presence throughout the story. His key relationship is with Onizuka, whom he treats with kindness and respect, unlike most of the faculty. His notable abilities are not combative; they involve his diverse artistic talents and his capacity to avoid the conflicts that consume other characters.