River Bed

Kawabuchi is a town where junior high school students drown one after another, it's also well known for a town where people die for 100,000. Ryuusei is a 13 years old boy who started to live there with his father after the early death of his mother. The afternoon of first day of school he with two of his new friends are led to the riverbank by a bunch of bully leaded by Uchida (a senpai from his school, after a loss in a game at the arcade. What awaits them?!