Episode 721 - Luffy's Supreme Trial! The Struggle for Liberty and Heritage

Episode 721
Luffy’s Ultimate Challenge! The Fight for Freedom and Legacy
Japanese: ルフィの究極の挑戦！自由と遺産をかけた戦い
Rufi no Kyūkyoku no Chōsen! Jiyū to Isan o Kaketa Tatakai

On the mysterious island, the crew learns about a legendary treasure hidden deep within its caves. However, a powerful and ruthless pirate crew arrives, intent on claiming the treasure for themselves. The Straw Hats must fight back to prevent the island from falling into the wrong hands, all while trying to uncover the island's true purpose.