Wildman Daisuke Yamamoto, raised in the Amazon Jungle, transforms into the Masked Rider-like reptilian mutant Amazon, and travels to Japan to fight the evil Gedon Empire, which completely slaughtered his jungle's inhabitants.

A Tarzan-like person from South America, named Daisuke Yamamoto, is awakened, and sent to Japan, because the villagers were all slaughtered. Daisuke makes new friends and allies, while fighting the forces of Gedon. Gedon needs Daisuke's GiGi Bracelet, because they have the GaGa Bracelet. The two Bracelets combined makes whoever possesses them a powerful being. Later in the series, Emperor Zero debuts his plans for destroying Japan.—Hongou