Miyanaga Saki is a first year high school girl whose family would get angry if she won the family mahjong games. But losing would also have its consequences. Because of this she develops a new way of playing that allows her to stay on the thin line between winning and losing, the +/- zero score, an almost impossible score. In a game that relies mainly on luck, the +/- zero score is harder than winning, but Saki can achieve this every time. Having always hated the game, her friend from middle school, Suga Kyotoro, forces her to play in the schools mahjong club. Her developed skill and superhuman luck has made her a worthy mahjong opponent, even to the middle school's national mahjong champion.
Nodoka Haramura's appearance on television playing in a high school mahjong tournament inspires her old Jr. high school friends to reform their schools club so they can meet and play her in the National High School Mahjong Tournament.