Kōji Yamada is the central protagonist of the anime Demon Warrior Koji, an adult OVA series based on a manga by Toshio Maeda. He is described as a man-demon, suggesting he possesses both human and supernatural traits. His primary role in the story is to hunt down preternatural killers, specifically a monster responsible for a series of extreme dismemberment murders. He is aided by a morbid psychic, who assists him in following the grisly trail of victims to a lonely woman. His abilities are not detailed in available sources, but the implication is that his demonic nature grants him the power necessary to confront supernatural threats. Koji operates within a team of misfits known as the Sex Murder Investigation Unit, though the exact nature of his relationships with other members is not expanded upon. The narrative centers on his investigation and confrontation with the supernatural killer, making him the driving force of the plot. No further background, personality traits, motivations, or character development are clearly documented in the search results.