Yôichi Minamikawa

Hideaki and his 6th grade classmates Takeshi, Chie and Tetsuya, wake up to find themselves in their old elementary school after the suicide of their teacher. They are forced to torture one another by playing X Game, which was created by Takeshi to bully a girl named Mariko. (imdb)

A series of murders occur where girls are killed but the criminals are also killed, making it difficult for the police. However, the only thing they know about them is that it has to do with a game about a virtual girlfriend named Erika.