On a future Earth ruled by Emperor Darius, the crew members of the Nautilus Submarine fight bravely to win freedom from oppression.

Magical Princess Minky Momo is waiting for a train to take her to her final destination when she encounters an old man who is waiting for a reunion. When she discovers he has left his passport behind in the station, she embarks on the train to try to find him -- in the process running into her previous self.