The Gum-Gum Fruit (Gomu Gomu no Mi) turns the user’s body into rubber. Luffy uses it to stretch, bounce, and punch with crazy power. What started as simple rubber powers evolved into Gear 4’s raw strength and Gear 5’s wild, cartoon-like abilities.
In Gear 4, Luffy uses Haki to inflate his muscles and compresses them with Armament Haki, turning into a bouncy, high-speed powerhouse called Bounce Man (Boundman). His body becomes rubbery and tank-like, giving him insane power and mobility. Moves like King Kong Gun and Rhino Schneider hit like a truck, literally.
Gear 5 unlocks the true nature of Luffy’s fruit—The Sun God: Nika (Hito Hito no Mi). This form lets him fight freely, cartoon-style, with outrageous powers that ignore logic. Luffy becomes all rubber and laughter, stretching reality itself. It’s his most chaotic and creative form yet. Basically a living Looney Tune with haki.