High roller Yumeko Jabami plans to clean house at Hyakkaou Private Academy, a school where students are evaluated solely on their gambling skills. Reigning class gambling champion Mary attempts to hustle unsuspecting transfer student Yumeko Jabami into a high-stakes game of rock-paper-scissors. Mary is relegated to the lowest levels of the gambling hierarchy after her loss. Student board member Itsuki challenges Yumeko to a game of pairs. To regain her status, Mary duels student board member Yuriko in a game of “life or death.” With Mary’s crushing defeat, Yumeko offers to play next.