As the Straw Hat Pirates arrive at Delta Island for the exhilarating Pirate Fest, organized by the cunning Buena Festa, they become entangled in an elaborate plot that promises both adventure and danger. Festa sends them on a quest to a floating island, supposedly in search of a legendary treasure that once belonged to the famed Gol D. Roger, the Pirate King. What ensues is a tumultuous clash as various pirate factions, including the infamous Worst Generation, embark on an adventurous journey through the Knock Up Stream, engaging in extreme battles and underhanded tactics to seize the coveted treasure. However, this entire spectacle is revealed to be a clever deception orchestrated by Festa in league with the mysterious Douglas Bullet, who recently escaped the confines of Impel Down, a prison that had held him captive for twenty long years.
At the same time, Trafalgar Law starts to unravel Festa's sinister scheme, managing to evade a fierce attack to alert his crew aboard the Thousand Sunny. He finds allies in Robin, Sanji, Chopper, and Brook, as well as the stealthy Smoker, as they delve deeper into Festa's dark plotting. Upon infiltrating Festa's stronghold, they stumble upon an alarming truth: Festa has struck a deal with the Marines to unleash a catastrophic Buster Call on Delta Island, dooming its inhabitants to destruction.
The treasure hunt climaxes as the pirates finally grasp their prize, only to be met with the devastation of Bullet's massive ship, leading to the destruction of the floating island. As they fall into the surrounding waters, Bullet claims the treasure and audaciously challenges the Worst Generation. Luffy and his crew find themselves quickly outmatched by Bullet's overwhelming strength and the unsettling powers of the Clank-Clank Fruit. In a moment of desperation, Usopp intervenes, drawing Bullet's focus away, giving the remaining pirates a chance to escape the impending danger of Delta Island.
Amidst their hasty retreat, an unexpected threat emerges: the Marine Buster Call fleet approaches, mercilessly closing in on them. In the turmoil, Law's group encounters Smoker within Festa's lair, prompting a brutal confrontation between Sanji and Smoker while Law and Robin make their escape. Sanji’s candid admission about Festa's orchestration of the Buster Call shocks Smoker, who grasps the level of manipulation at play.
Meanwhile, Law and Robin encounter the enigmatic Crocodile, a former Warlord, who extends an alliance with Law, embroiling him in a higher-stakes game. Away from this unfolding drama, Bullet amasses power to face down the approaching Marine fleet, unleashing his awakening Devil Fruit abilities to annihilate the forces sent against him, altering the landscape into a monstrous entity that overpowers both pirates and Marines alike. Festa, manipulating the chaos, unveils that the treasure is an Eternal Pose, directing ships towards the legendary Laugh Tale, the location of the ultimate treasure coveted in the world of One Piece. This vision drives Bullet's ambition to usurp the title of Pirate King.
As Marine Fleet Admiral Sakazuki orders another Buster Call, Luffy's group finds their way back together. Sanji, Robin, Chopper, and Brook converge, with Chopper tending to the injured Luffy and Usopp. Upon awakening, Luffy is determined to confront Bullet but is quickly overwhelmed by the raw power he faces.
The daring Warlord Boa Hancock seeks out Luffy but encounters an eclectic assembly of characters including Buggy, Smoker, Law, and Sabo. Law discloses his strategy to dismantle Bullet’s imposing behemoth, now including Crocodile and Rob Lucci in this quest. With united efforts, they manage to dismantle part of Bullet's colossal creation. Luffy, empowered by his Gear Fourth, manages to obliterate the opposing limb, while Usopp's sharpshooting adds to their assault.
In a climactic fistfight, Luffy battles Bullet and triumphs, however, Crocodile and Lucci make a play for the Eternal Pose only for Luffy to thwart their intentions by destroying the treasure. He resolutely declares that he and his crew will seek out the legendary One Piece on their own terms, without reliance on shortcuts.
As Festa contemplates his dwindling schemes, he finds himself at the mercy of Sabo. Meanwhile, Luffy is finally reunited with his trusted crew who are eager to escape the chaos looming over them. Just as hope wanes, Smoker discreetly informs his superiors that the Buster Call's mission is now moot, thus allowing Sabo's extraordinary capabilities to guide the pirates to safety through the collapsing fleet. In the aftermath, a monumental secret unfolds revealing that Roger had intentionally dismissed the Eternal Pose, viewing it as contrary to the essence of true pirating—one unbound from traditional means of pursuing one's dreams. This profound revelation impacts Luffy's crew greatly, evoking a mixture of shock and reverence. Yet, amidst this realization, Usopp retains his unwavering spirit. With characteristic resolve, Luffy proclaims that clinging to the Eternal Pose would have led them to miss out on countless adventures, resonating with his unyielding spirit of freedom and invigorating a renewed sense of exploration among his crew.
