Monkey D. Luffy first uses during the Dressrosa Arc in his climactic battle against Donquixote Doflamingo. Anime Debut: Episode 726, titled " Gear 4! The Phenomenal Boundman! Manga Debut: Chapter 784, also titled "Gear 4".
Monkey D. Luffy unveils this transformation during the absolute climax of the Dressrosa Arc to break the ultimate stalemate against the Warlord of the Sea, Donquixote Doflamingo. The Moment of Reveal: Dressrosa Arc
A punch that can change direction in mid-air to "chase" an opponent. Leo Bazooka: A massive double-palm strike.
And when we finally see it against Doflamingo, it’s not a triumphant reveal. It’s a . Luffy’s eyes go dark. His body inflates into something almost grotesque — a caricature of power. He even jokes about it (Boundman), but you can feel the weight: this form is a burden. It shortens his lifespan. It nearly kills him after one use. when do we first see gear 4
While the combat debut occurs in Dressrosa, the concept was retroactively introduced during the Whole Cake Island Arc.
On the surface, the answer is simple: Episode 726 / Chapter 784 — Luffy vs. Doflamingo, Dressrosa.
Note: The transformation was teased at the very end of Chapter 783. Monkey D
Realizing his current strength fell short of protecting his friends and the citizens trapped inside the closing Birdcage, Luffy confidently declared he needed a technique to completely overwhelm his opponent. At the end of Chapter 783, he utters the words: "Gear Fourth."
Why did Gear Fourth appear at this specific moment? The narrative necessitated a power capable of bypassing Doflamingo’s defenses, which previous forms could not achieve.
Doflamingo was capable of tracking Gear Second’s speed. However, Gear Fourth’s "Boundman" form alters Luffy’s trajectory. By compressing his body into the ground or air, Luffy achieves a chaotic, bouncing movement pattern that is difficult for observation Haki users to predict. The Phenomenal Boundman
The core mechanic of Gear Fourth is described by Luffy as "Muscle Balloon" (Kinniku Balloon). Luffy blows a massive amount of air into his muscular structure rather than his bones. This results in a torso that appears round and robust, with his limbs becoming coated in an incredibly dense layer of muscle.
A compressed punch that sent Doflamingo flying across Dressrosa. Rhino Schneider: A powerful flying dropkick.