Hideo Aiba's dull existence turns exciting when Kurumi Sahana transfers into his class. Petite and mysterious, Kurumi instantly becomes the center of the entire school's attention. Aiba is overjoyed when she joins the occult Roman Club—consisting of the newly appointed president Aiba himself, the four-eyed Katsu Toshitsuku, and the chicken-hearted Tatsuya Yatsu.

Unexpectedly, Kurumi wishes to start a purely physical relationship with Aiba—but only if he does whatever she wants, and they will never have sex. Madly in love, Aiba happily agrees to be her partner.

Joined by their anus-loving ex-president and the candid airhead Kyouko, there is rarely a boring day in the lives of the Roman Club members, whether they are scouring secluded places in search of ghosts and aliens or simply hanging out in the clubroom. All the while, Aiba's feelings toward Kurumi continue to deepen as the two satisfy each other's perverse desires. But despite their intimacy, Kurumi seems to be hiding something from Aiba.