Luffy and his crew found a treasure chest in the ocean, only to be disappointed to find an old lady in it. The old lady, Roba, guides the crew to the Mecha island where they meet the leader of the island, Ratchet. Karakuri Castle is yet another treasure-hunting epic for the Straw Hats, taking place after Episode 228 during the Foxy’s Return Arc in the Water 7 Saga.