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.

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.

Jo, the water polo captain, proposes that the team creates an original jersey. But emotionally attached to his own, Amihama declines saying, "I don't need a jersey."

While watching a video, Minato sees his past self from before he lost his memories. When asked about it, Chinu reveals her motives for keeping quiet about the truth. After hearing what she says, Minato is shocked beyond words.

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.

With one month left till the prefectural tournament, Minato directs the others on how they should train while starting a regimen of his own to work on getting his groove back. He and the team have a lot on their minds as the days dwindle down.

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.