The film's central mystery revolves around Gol D. Roger's lost treasure, which is revealed in the climax to be an Eternal Pose leading directly to Laugh Tale—the location of the One Piece. Douglas Bullet's master plan is to use this prize as bait to gather the world's strongest pirates and Marines in one location, only to slaughter them all to prove he has surpassed Roger.
In his awakened Devil Fruit form, Bullet creates a colossal mechanical titan that forces an unlikely alliance: Luffy, Law, Sabo, Boa Hancock, Buggy, Smoker, Crocodile, and Rob Lucci all team up to break his defenses. The crucial turning point occurs when an earlier, seemingly ineffective plant attack by Usopp blooms inside the titan, destroying Bullet's armor. In a final clash of Conqueror's Haki, Luffy defeats Bullet.
The ultimate twist happens when Luffy secures the Eternal Pose, only to crush it in his hands. A post-credits scene reveals that Roger himself threw the pose into the sea decades ago, considering it useless because his crew was 'too early' to fulfill the world's destiny, perfectly echoing Luffy's desire for a genuine, unguided adventure.