Kamiyama High School. Rui Kamishiro, a handsome but incredibly quiet and timid boy, attends this school. He cries at the drop of a hat. Because he cannot blend in with others, Rui naturally began to be marginalized. Always alone, always the one left over when forming groups for projects, he became a presence as thin as air.

Whether out of pity or concern for Rui, the teacher asked Guest, the class president, to look after him.