A P.E. teacher, Nikusuke, happened to obtain a brief of "Dark Rhythmic Gymnastics Project". It is a competition where the players compete with others their lewdness. Following the project, Nikusuke looked for the players with Tomomi, a granddaughter of the board chairman. Their first game was Miku. Tomomi deceived innocent Miku, and she invited Miku out at night.

(Source: AnimeNfo)