Youthful Prelude.As Eruna Ichinomiya, a somewhat perverted schoolgirl, is pressured into choosing a high school, her cousin, Shigure Ninomiya, recommends his school, Mikagura Private Academy. Taking an interest in the principal's granddaughter, Seisa Mikagura, Eruna decides to take the entrance exam, which she passes by being able to see the school's feline teacher, who she names Bimii. At the start of her new school life, Eruna learns about the school's system, in which students are required to join one of the school's clubs, using points earned by battles against other clubs to improve their state of living. Stuck with the poorest living conditions due to not yet being in a club, Eruna attempts to join Himi Yasaka's Calligraphy Club, but is rejected due to her poor art skills. A few days later, however, Eruna is approached by Seisa herself, who invites her to join her Going-Home Club on a trial period on the condition that she act as the club's representative in a battle taking place the next week.