Ao Oni is an enigmatic, mysterious creature that lives in the abandoned mansion on the outskirts of a town in Japan. He was originally a dude from the town that went to the mansion and died leading him to become the Oni, or in my theory, became the Oni due to the water in the bathtub. He's from a puzzle RPG horror game. He murdered 3 of 4 children. The children's names were Hiroshi, Takeshi, Takuro, and Mika with Hiroshi being the 4th that survived.