In a seaside village where little happens, middle schoolers Keisuke Isobe and Koume Satou live a dreary life. But when Koume's crush breaks her heart, their position changes. She begins a "no-strings-attached" relationship with Keisuke, whom she had rejected, to fill emotional shortages in their life. "Friends with benefits" becomes tricky when actual feelings arise and their relationship affects others and themselves. Umibe no Onnanoko examines love, relationships, and the emotional cost of a decision between two teens.