Unlike his previous "Gears," which focused on blood flow (Gear 2) or bone inflation (Gear 3), Gear Fourth operates by while coating it in dense Armament Haki.
“How long can I stay in it now?” he wondered. “Thirty minutes? Forty? Maybe one day… one day I’ll use it and not deflate. One day, my body won’t betray me after the fight.”
He’d punched the gorilla. The shockwave cracked the mountain behind it. But then he deflated. He collapsed. For an hour, he couldn’t move. He was a shriveled, gasping doll in the mud, watching ants crawl over his fingers. For the first time in his life, Monkey D. Luffy felt vulnerable . He hated it.
He looked normal. Bony knuckles, rubbery skin, the small scar under his palm from a fight with a sea king when he was seven. But he could still feel it. The ghost of Gear Fourth. gear fourth
Since you didn't specify a particular medium (like a YouTube script, a blog article, or an in-game ability breakdown), I have designed this as a suitable for an anime review site or a lore deep-dive.
This form is terrifying to opponents. Luffy loses his lean agility in exchange for a bouncy, tank-like stature. He cannot stand still; he must constantly bounce. This movement is disorienting for enemies, as he can use the compression in his legs to launch himself into the air, effectively flying (or rather, walking on air) by kicking the air with the force of a cannon.
He jumped to the figurehead, placed one sandal on the lion’s mane, and screamed into the coming storm: Unlike his previous "Gears," which focused on blood
This is the default and most powerful form. It focuses on and physical resilience.
And yet.
Perhaps the most compelling aspect of Gear Fourth is its cost. In anime, power-ups often come with little drawback. Gear Fourth, however, drains Luffy’s Haki reserves at an alarming rate. It is a "timer" form. The shockwave cracked the mountain behind it
: Once the form ends, his Haki is completely exhausted for 10 minutes, leaving him defenseless in a "cooldown" state.
Gear Fourth is one of the most powerful forms of Monkey D. Luffy, introduced during his battle against Katakuri on Whole Cake Island. This form is a significant advancement in Luffy's Gear Fourth transformations, showcasing not only enhanced physical abilities but also a strategic approach to combat.