Hyakkaou Private Academy, one of Japan's most prestigious schools where, unlike normal schools, the hierarchy is determined by gambling. Yumeko Jabami is a transfer student whose beautiful, innocent facade hides a psychotic addiction to gambling and high-stakes situations.

With a keen intellect able to pierce through the elaborate cheating methods used by the most powerful students to rig games in their favor, Yumeko threatens to destroy the twisted hierarchy of the school simply for the thrill of it.