Ichinomiya Eruna is a third-year junior high school student who has not decided on which high school to attend, and spends her days skipping school and playing games at home. One day, Eruna's eyes are captivated by a photo of Mikagura Seisa in a pamphlet for Mikagura Private Academy, given to her by her cousin, Ninomiya Shigure. Feeling that it is fate, Eruna decides to attend Mikagura Academy.

However, as Eruna discovers, all students must belong to a club there, and that an intense club battle system pits students with special powers against each other. The outcome of these inter-club struggles determines the club's rank, and the status of its members; meaning the quality of their accommodations and food. So the club-less Eruna has to content with a sleeping bag and a very simple dish, for now... until she encounters Seisa, and is invited to join her going-home club.

[Source: AniDB]