Nori visited her aunt's apartment by the sea for the first time. She found a postcard letter from her aunt's notebook by accident. It was from Mitsuko Miyoshi. She decided to visit the unknown woman's address.

Reiko, who has retired from acting, now lives with Masao, an illustrator. Meanwhile, Mitto, a childhood friend and former idol, shows up at the studio of Tamade, a cameraman, bringing her pet Betta fish along. Mitto says she is planning a performance event in order to self-publish a novel. Reiko and Tamade, along with Masao, each become involved in Mitto’s event in their own way. The appearance of Mitto brings a subtle change to the future path the three of them will walk. This is the story of four people and a fish, intertwining their lives in unexpected ways.