Shinomiya Yuri and Usami Nana are close friends and belong to the same club, which is overseen by their teacher Kohaku Uta. Nana secretly harbors romantic feelings towards Yuri, but these feelings aren't reciprocated. As punishment for their behavior in class, they are made to visit Kohaku's home for private study sessions. During one of these visits Kohaku secretly puts sleeping pills in their tea, and subsequently confines them and subjects them to various forms of punishment.