One Piece Movie 7: Karakuri-jou no Mecha Kyohei

One Piece: Karakuri Shiro no Mecha Kyohei

Karakuri Castle's Mecha Giant Soldier

ワンピース THE MOVIE カラクリ城のメカ巨兵

The Straw Hat crew salvages a treasure chest from a sinking wreck, inside which they find an old lady. To get the pirates to take her home, she promises them the treasure of a golden crown on her island: Mecha Island. Upon arrival, the crew is attacked by the lord of the island but he has a change of heart and decides to seek their help to solve the mystery of the Golden Crown.

(Source: ANN, edited)