A recently dumped free spirit and an unlucky businessman unexpectedly meet on the way to a beach and start staying at a small guest house by the sea.
Kaito's girlfriend comes to the Diamond Head, as does Hiromi's ex. That night, Kaito learns that Hiromi was once a swimmer with Olympic aspirations.
Kaito returns to his company to work on a project. Hiromi sets out for Tokyo to do a favor for Masaru but finds an unexpected passenger in his car.
Kaito's former boss arrives at the guest house to find out why Kaito would give up his career. Makoto learns that Masaru wants her to meet her mother.
A man arrives at the Diamond Head saying he's the swimmer who went to the Olympics in Hiromi's place — and that he wants to settle things with a race.
Ahead of an annual fireworks show, Kaito feels dejected when Sakura decides not to come. Haruko alters an old summer robe to give to Makoto.
Masaru brings a regular guest named Michie to the Diamond Head. She immediately takes charge and puts everyone to work cleaning up the guest house.
As summer nears its end, Makoto grows anxious that Kaito and Hiromi will leave soon. Kaito offers to tutor Makoto's struggling classmate.
Haruko gets a letter from her ex-husband saying he is bringing their son to meet her — and that he has not told the boy that she is his mother.
With the guest house now empty, Masaru takes Hiromi and Kaito on a fishing trip. Haruko encourages Makoto to reach out to her estranged mother.
Masaru attempts to surf again but wipes out. Hiromi and Kaito lend their support as he begins training so he can try catching a wave once more.
The Diamond Head's future becomes uncertain. Hiromi and Kaito resolve to follow Masaru's advice, and Haruko makes a decision about the guest house.
