Hitoha, the youngest of the Marui triplets, frequently gets into trouble with her sister Futaba, who likes the sensation of playing with her soft cheeks. Hitoha's predicament worsens when a pimple resembling a breast appears on her cheek, and she begins attracting unwanted attention at school. Meanwhile, the oldest sister, Mitsuba, messes with sports equipment, putting herself in tough situations. No matter the circumstances, the sisters' time together never grows dull.