Nobita and his father purchase a large rhinoceros beetle, with Nobita pledging to his father to properly care for it. Subsequently, Doraemon's squad chances upon a peculiar island hosting a tribe that lives alongside ancient creatures that were assumed to be long extinct, but were instead safeguarded by a legendary beetle entity known as Golden Hercules. Nonetheless, the squad becomes embroiled in a conflict with a band of time-travelling felons who are set on seizing Golden Hercules for financial gain.