Kishimoto Kasumi, a 15-year-old girl, was scheduled to move in with her aunt in April to attend high school. However, upon arriving at the house, she was surprised to find that four new male students were already living there. To make matters worse, while she was taking a bath that day, Takasugi Yusaku, one of the boys, entered the bathroom and saw her naked. This is how Kasumi's troublesome high school days began.