When a border guard with a sixth sense for identifying smugglers encounters the first person she cannot prove is guilty, she is forced to confront terrifying revelations about herself and humankind.

The son of a sailor, 5-year old Sosuke, lives a quiet life on an oceanside cliff with his mother Lisa. One fateful day, he finds a beautiful goldfish trapped in a bottle on the beach and upon rescuing her, names her Ponyo. But she is no ordinary goldfish.