Arata Kasuga enrols in the Royal Biblia Academy and meets the Trinity Seven, a group of female magic users.

While doing research, Arata and three of his classmates get locked inside a sealed room. With no exit to be found, the group find themselves in desperate need of the bathroom.

The group spend some time at the beach, where they enjoy the hot springs. Arata discovers that he must choose his Theme to prevent disaster.

When a power leaks from beneath the school, Arata and the gang go down into the labyrinth to save the school from the collapse phenomenon.

When a ghost suddenly appears in the library, Arata and the gang go to investigate and are transported to the Eternal Library.

When another breakdown occurs, the group realises that it was caused by a member of the Trinity Seven.