Nishihama Junior High School is haunted by the legend of Sayoko. Every three years a student is chosen to play the role of Sayoko by his or her predecessor. Sayoko has three missions to accomplish. If they are completed it is to the advantage of the school. If not, the school is doomed... Shu has been chosen to be Sayoko. Disbelieving the legend, Shu lets his pal Rei assume the role. But, when the new term begins, one of the tasks has already been completed. By whom? This is just the prelude to a string of spooky happenings.

　　在西濱國中有個不可思議的傳說，就是每三年一定會出現一個「小夜子」，而小夜子必須完成三項任務，否則全校師生將會遭遇不幸。潮田玲（鈴木杏飾）因為非常想成為「小夜子」，便自作主張代替真正的小夜子，準備悄悄完成這些任務。就在此時，有一位神秘的轉學生沙世子（栗山千明飾）出現在小玲面前…