Young college student Shinn Akatsuki returns to his high school as an adviser for the underperforming mathematics student, at the apparent request of the principal. Although an impeccable and courteous man on the outside, Shinn hides a very dark side to him: as part of his unending perversion, he enjoys seeing girls that he considers "out of everyone's league" succumb to him. Never satisfied before, however, he discarded his past victims. But now, Shinn decides to create his "ultimate sex harem", and with these dark thoughts in mind, and selects the candidates he considers "ideal" as he becomes acquainted with the school: the star of the track and field team, the innocent and tomboyish Makoto Shinjugai, the rich and spoiled tennis player Ritsuko Yasuhiro, the graceful, serious and traditional Satsuki Katsuragi, the swimming team's promising, dutiful and charming Aina Aozaki, and the basketball star, Touko Takatsukasa. As he begins his "hunt", Shinn also adds gymnastics instructor Rina Akiyama to his lust after she impresses him with her luscious body and maturity.
And thus, under the pretense of a "responsible adviser" and the help of his one remaining past sex lover, professor Reika Tohno, the protagonist's wicked quest to create his ideal sex harem begins...