Episode 660 - Luffy's Vow! The Inheritance of the Pirate Monarch

Episode 660
Luffy’s Promise! The Legacy of the Pirate King
Japanese: ルフィの約束！海賊王の遺産
Rufi no Yakusoku! Kaizoku-Ō no Isan

The Straw Hat Pirates solve the temple’s puzzles and uncover a shocking revelation about the treasure they’ve been seeking. The treasure is revealed to be a powerful weapon capable of changing the fate of the Grand Line. As they prepare to leave the island, they realize that they are not the only ones who know the truth about the weapon.