Minato Kiyomizu wakes from a coma following a car accident. Though once a water polo star in junior high, he's lost three whole years of memories. Abandoning any hope of playing again, he enters Yamanami High School an entire year late.

Minato learns from Chinu Kawakubo about a promise they made in the past. To fulfill their promise, he decides to join the water polo club, much to the delight of Eitaro Oka and the team captain, Jo Jojima. They utilize his fame to recruit members, but...

Takekazu Ejiri, Yutaka Babayaro Inomata, and Yoshiharu Ushimado join the club, but it needs one last person to make seven for a regulation team. They ask Shugo Amihama, who swam in junior high, but he refuses. When they persist, Shugo makes a proposal.

Amihama stubbornly refuses to join, but a certain something changes his mind and Yamanami's Water Polo Club is officially underway. Despite the team struggling with the basics, they find themselves playing their first practice match.