Shuutarou Maruki, lives an ordinary school life as a newly appointed teacher. However, he's had a hidden fetish that he could not tell anyone: a true masochistic temperament. Living with his brocon step-sister Komugi, Shuutarou has had to suppress those desires in order to lead a peaceful, though boring life. Suddenly, two beautiful girls appear before Shuutarou: Mafuyu and Natsuhi Kido. They are his estranged younger sisters, separated from him at childhood. The girls, who have now come to be Shuutarou's students, approach him with their sadistic side ready to make his dormant masochist side blossom again! And so begin the exciting days with three sadistic beautiful girls!