Did you see? The jungle's still here!

"Amazon" (アマゾン?, portrayed by Tōru Okazaki), whose real name is Daisuke Yamamoto (山本 大介 Yamamoto Daisuke?), was an infant around the time of the plane he and his family were on crashed in the Amazon rainforest, leaving young Amazon the sole survivor and grew up as a wild child.

However, Amazon's idyllic existence is cut short when Gorgos, the Ten Faced Demon, massacres a village in search of the powerful "GiGi Armlet", which gives the bearer fantastic power. Elder Bago, last of the Incas, gives the GiGi Armlet to Amazon for safekeeping while using his knowledge of Incan science and magic to perform a mystical "operation" on Amazon, transforming him into the powerful "Kamen Rider Amazon" before he died.

Though in the first half of the series, becaused he was isolated from any human contact as a child, amazon could not speak coherent Japanese and say only a few words. But through Masahiko helping him cope with the culture shock, Amazon/Daisuke learned to speak properly.