In the 1960s in the Kashima area of Ibaraki Prefecture, Japan, the era of rapid economic growth, a fisherman's family strives to make a living through the construction of Kashima Port and fishing in Kashima Bay. Based on a true story, this fantasy tale intertwines the family's struggle with the legend of sea turtles passed down in the local community, alongside the coming-of-age journey of the young boys.