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.