Himoto Sora is a transfer student with a sense of justice and dreams of becoming a knight. Upon arriving at Utopia Gakuen, she learns of a virtual reality-like game played by the male students in which they use girls as weapons in battles for status and treat them as commodities. Seeing one of these girls being abused she steps in and through some sort of error unwittingly becomes the first female participant of the game.

Hyakkaou Academy, a prestigious private school. Here in this academy, students are divided into social strata. Standing above all others is the student council, who rules over the students with their Gambles. It's heaven if you win, and hell if you lose. Those adept at gambling are the envy of all, while the weak are left to suffer the madness of the academy. One girl transfers to this academy. Her name is Jyabami Yumeko.