When Satoshi Yabe, the newest teacher at an elementary school, is assigned as the homeroom teacher of class 6-3, he is in for a shock. The class is full of chaos and eccentric students, but none are more troublesome than the mischievous Marui triplets. Mitsuba is sadistic and unusually mature for her age; Futaba is both lewd and incredibly strong; and Hitoha, often absorbed in her erotic books, is quiet and ominous.

As the sisters take an interest in Yabe, they start pestering him with endless antics. With misunderstandings and bizarre situations unfolding every day, Yabe's life at school is anything but boring.