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.

Hoping for their first win at the summer prefectural tournament, the club holds a training camp during Golden Week. The team is getting along and there are good vibes all around, but all the while, something weighs on Ushimado's mind.

Eitaro tries to persuade Minato to rejoin the water polo club. Wanting no part of it, Minato is frustrated at being compared to his past self and his failure to become Shogakukan's ace.

The Yamanami water polo club nervously faces the day of the prefectural tournament. Minato spearheads the team as they battle Rikka Gakuen in the first match, but their opponents have come up with a strategy to keep Yamanami from going on the attack.

It's finally time for their second match of prefecturals--the long-awaited showdown with Shogakukan. Minato, Eitaro, Jo, Amihama, Ejiri, Babayaro, and Ushimado join their seven hearts as one and challenge the best team in Japan.