One Piece Movie 07: Karakuri-jou no Mecha Kyohei

After the Straw Hat Pirates pull a treasure chest from a sinking ship, their hopes of riches vanish when an elderly woman climbs out instead. She persuades them to return her to Mecha Island by promising a legendary Golden Crown hidden somewhere on her home.

The island's eccentric ruler, Ratchet, first greets the crew with hostility, then decides their strength may be useful in solving the crown's ancient riddle. Luffy and his friends follow a trail of mechanisms, songs, and clues beneath the island, unaware that the treasure hunt is tied to a much larger secret and to Ratchet's own dangerous ambitions.