Amano Aki goes with her mother Haruko to her hometown in Kitasanriku during a summer vacation. There, she meets her maternal grandmother, Natsu, for the first time. Natsu is a woman diver aka "ama", and Aki thinks that is just so cool. Aki is a second-year high-school student, and she struggles to keep up with the fast-paced life in Tokyo. Having been confined indoors most of the time, everything she sees in the rural town is exciting to her. But most of all, seeing her grandmother diving under the fierce surf along the coastline, leaves a huge impact on her. "I think I would like to be a diver too..."