One day, while battling a rival pirate crew, the Straw Hat Pirates encounter a strange boy with a seahorse-like instrument. The sound of this instrument instantly knocks all of the Straw Hats unconscious; when they awake, they find themselves - along with the Going Merry - on an uncharted island, with no memories of who they are, what they do, or even how they fight.
Beset by enemies from all sides, the Straw Hats must accept the help of an old enemy-turned-friend in order to survive, solve the mystery of the island, and retrieve their memories.
- The Isle Unremembered (記憶に無い島 Kioku ni nai shima?)
- Twin Cape (ふたご岬 Futa go misaki?)
- Whiskey Peak (ウイスキーピーク Uisukī pīku?)
- Little Garden (リトルガーデン Ritoru gāden?)
- Drum Island (ドラム島 Doramu-tō?)
- Keimi and Pappug make their first in-game appearances, albeit with different color schemes than in the anime. The Goldfish Princess also appears in this game too.