Hideo Aiba's mundane life becomes thrilling when Kurumi Sahana transfers into his class. Small and enigmatic, Kurumi immediately captures the attention of the entire school. Aiba is delighted when she joins the occult Roman Club, which includes the newly appointed president Aiba himself, the bespectacled Katsu Toshitsuku, and the cowardly Tatsuya Yatsu. Unexpectedly, Kurumi wants to begin a purely physical relationship with Aiba—but only on the condition that he obeys her every whim and they never have sex. Hopelessly in love, Aiba gladly agrees to be her partner. With the addition of their anus-obsessed former president and the blunt airhead Kyouko, the Roman Club members rarely experience a dull day, whether they are exploring remote locations in search of ghosts and aliens or simply relaxing in the clubroom. Meanwhile, Aiba's feelings for Kurumi continue to grow as the two fulfill each other's perverse desires. Yet, despite their closeness, Kurumi appears to be concealing something from Aiba.