Since April, Kishimoto Kasumi, a 15-year-old girl, was scheduled to reside at her auntie's house in order to attend high school. However, when she moved into the house, she was astonished to find four new male students residing in the same house. To make matters worst, as she was taking a bath that day, Takasugi Yusaku, one of those lads, stepped in and saw her naked. This is how Kasumi's tumultuous high school years began.