The Devil's Fist - A Show Down! Luffy vs. Grount

Prodi confronts the rescue party at the coast, desperate to protect his base's fearsome reputation, since a defeat would cost him a demotion and the comfortable pension he is counting on. He fires his bazooka at the Shark Submerge III, seemingly engulfing Brook in the blast, then turns the weapon on the team, boasting that he once dueled Garp on even terms with it. As the Marines press in, their rubber-coated shields shrug off Nami's Thunderbolt Tempo and Carrot's Electro, so Nami scatters them with Gust Sword and Mirage Tempo while Chopper crushes them in Kung Fu Point and Carrot delivers an ordinary kick. Luffy weaves around the bazooka fire and downs Prodi with a Gear 2 strike.

By the warehouse, Grount sulks that he is too weak to join the fight, drawing angry rebukes from Bonham and Zappa about the training they shared under Aokiji. A flashback recalls the day a young Grount, unable to control his giant red arm, devastated a city; Aokiji investigated, dodged the boy's wild strikes, and froze the limb. Years of training followed, with the arm sealed in a metal casing, and Aokiji told Grount to keep honing it for the strong foes ahead.

Luffy beats Bonham and Zappa with Jet Gatling, and Brook reveals the Submerge survived Prodi's attack intact. As the team moves to leave, Grount springs out and tells Bonham and Zappa that this duel belongs to him alone. Steam pours from his arm, the casing crumbles, and his fully controlled monstrous limb is bared. He overwhelms Luffy with its sheer force until Luffy answers with Gear 3, matching him. When Grount sends him flying, Luffy keeps his Haki-clad Gear 3 and unleashes Thor Elephant Gun; the two enormous fists collide and rock the coast before Luffy gains ground and smashes Grount into the beach. Waking later beside Bonham and Zappa, Grount laughs that Luffy earned his bounty and vows a rematch.

This is the closing episode of the filler Marine Rookie Arc. Luffy defeats Vice Admiral Prodi as well as Bonham and Zappa, a flashback shows how Grount first encountered Kuzan, and the Captain finally lets loose his monstrous limb at full strength. The bout between Grount and Luffy is their third, and Luffy emerges victorious. The crew departs the Fron Island base with the stolen rations, then devours every bit of it within ten minutes; much was eaten by the long-starved Pedro and Pekoms, though even the crewmates who had already eaten on the island joined in.