The episode itself is a masterclass in anime escalation. After being launched into the atmosphere, Luffy bites into his own arm—a callback to how he inflates his bones for Gear Third. However, this time, he does not blow air into his bones but rather into his . The result is visually shocking: Luffy’s arm swells to colossal proportions, followed by his entire torso and legs, transforming him into a hulking, bouncing titan covered in dark, swirling patterns of Busoshoku Haki (Armament Haki). The technique is named Gear Fourth: Boundman .
Since its debut, Gear 4 has become a staple of Luffy's combat arsenal, featuring multiple specialized forms for different high-stakes battles. Key Episodes for Gear 4 Forms which episode luffy uses gear 4
| Form | First Appearance (Episode) | Arc | | :--- | :--- | :--- | | Bounce Man | Episode 726 | Dressrosa | | Tank Man | Episode 807 (Vs. Cracker) | Whole Cake Island | | Snake Man | Episode 870 | Whole Cake Island | The episode itself is a masterclass in anime escalation
Luffy's Gear 4th form debuts in the anime episode: The result is visually shocking: Luffy’s arm swells