On the last day of summer vacation, Nobita finds a mysterious ocarina that summons a whale named Gony, who responds to a unique 52-hertz sound. Traveling back 7,000 years, Nobita, Doraemon, and friends discover a lost island civilization and meet Pito, the ocarina’s true owner. They learn that Gony is Pito’s beloved companion and join forces with him to protect the island from a looming crisis, unraveling the mystery of the ocarina and the vanished civilization.