Chapter 784 is titled "Gear Fourth".
Color Spread: Picnic with zombies.
The gladiators begin moving toward the King's Plateau, as Roronoa Zoro reveals to Kanjuro and Kin'emon that he is going to try to stop the Birdcage. Meanwhile, Monkey D. Luffy activates Gear Fourth and continues to battle Donquixote Doflamingo. The Shichibukai, initially unimpressed, is quickly overwhelmed by Luffy, sending him flying. Doflamingo attacks again but is unable to bypass Luffy's defenses, and Luffy gains the upper hand on him.
The citizens of Dressrosa run from the Birdcage, which is not cutting through the rubble of the town but rather pushing it toward the center. Meanwhile, Baby 5 and the Corrida Colosseum gladiators notice the shrinking Birdcage and Sai tells the gladiators that are still standing to get the fallen gladiators back on their feet. As Viola, Hack, and Usopp climb down from the King's Plateau, Viola notices that the epicenter of the Birdcage is slowly shifting towards Doflamingo's location, meaning even the King's Plateau, which is at the center of the island, will be torn apart, causing Usopp to get scared and tell them to move quickly.
Meanwhile, Kin'emon and Kanjuro run after Zoro, asking him where they are headed. Zoro tells them that they are going to stop the Birdcage, shocking the two samurai. On the Flower Field, Cavendish marvels that the dwarves managed to stitch Law's arm back on and hopes that it will heal properly. Cavendish then tells Law that when he was in the Underground Trading Port, he had realized that if Luffy and Law managed to defeat Doflamingo, the effects would be felt all over the world and the two of them would become the center of the storm, and Law replies that is what they are after.
On the palace rooftop, Luffy begins activating Gear Fourth, kicking his sandals off. He then covers his left arm in Busoshoku Haki and blows into it, inflating the muscles and causing his arm to assume massive proportions. Luffy continues blowing, resulting in his entire torso becoming incredibly large. Gear Fourth: Boundman is finally activated, which causes Luffy to constantly bounce around. Doflamingo laughs, expressing his disappointment that Gear Fourth, which he expected to be an ace up Luffy's sleeve, was nothing more than Luffy using his elasticity to bounce around. Luffy replies that during his two-year training on Rusukaina, this form was necessary to subdue the beasts on it into submission. Doflamingo states that he is still confused as Luffy sinks his fist into his body, which astonishes the Shichibukai. Luffy then releases his fist as he strikes Doflamingo, the sheer force of which sends Doflamingo flying all the way toward the streets of Dressrosa.
Doflamingo's hard landing destroys several buildings and causes the fleeing Dressrosa citizens to stare in shock at Doflamingo lying on the ground. Doflamingo slowly manages to get up, and a Marine asks him how he got here. Doflamingo testily answers that he would also like to know, and his barely contained rage sends the panicked citizens fleeing, though they quickly realize with a shock that Doflamingo is on one side and the Birdcage is on the other. Doflamingo then stares up toward the palace as he sees with a shock that Luffy is using his elasticity to fly down towards him. Suddenly, Luffy disappears from sight, but quickly reappears behind Doflamingo as he dropkicks the Shichibukai. The citizens stare in shock at Luffy's action and become even more perturbed when they see Luffy bouncing down the street.
Doflamingo flies through several buildings before flying upwards in a rage, trying to understand Luffy's new form. Luffy quickly jumps up and attacks Doflamingo with Gomu Gomu no Culverin Cannon, but Doflamingo manages to evade the strike and flies behind Luffy, attacking him with Athlete. However, the kick does not penetrate Luffy's rubber body, even though it is covered in Busoshoku Haki. Luffy then repels Doflamingo as he attacks the Shichibukai again. However, this time Luffy redirects its path to follow an evading Doflamingo, succeeding in punching Doflamingo in the face.
- Franky's dancing with zombies in the color spread resembles the famous "Thriller" dance by Michael Jackson.
- Luffy demonstrates his Gear Fourth technique on Doflamingo.
- Luffy first developed this technique during his training on Rusukaina.
- Zoro plans to stop the Birdcage.
- Law's arm has been reattached by Leo and healed by Mansherry.
- The fight between Luffy and Doflamingo moves from the palace to the city.