Koume attends middle school in a small town on the shore. She gets dumped by senior student Misaki. Koume enters into an intimate relationship with Keisuke, who has an introspective personality and is in the same grade as her. In their past, Keisuke confessed to Koume that he liked her a lot. Koume and Keisuke continue their casual intimate relationship and Koume begins to develop feelings for Keisuke, but Keisuke tries end his relationship with Koume.
Meanwhile, Keisuke takes action as atonement for his older brother, who was bullied and committed suicide.
~~ Adapted from a manga of the same name by Asano Inio.