A plane crashes in the Amazon rainforest, leaving young Daisuke Yamamoto stranded without his parents. Soon adopted by an Incan tribe under the name "Amazon", he becomes a wild child, living off the land. However, his village is massacred by the Ten-Faced Demon Gorgos, who searches for the powerful GiGi Armlet to take over the world with it. The last Inca, Elder Bago, gives Amazon the GiGi Armlet for safekeeping and uses his knowledge of Incan science and magic to perform a mystic ritual on Amazon and transform him into the powerful "Kamen Rider Amazon" before dying. Now in Japan, Amazon battles the evil organization Gedon, unaware of why they pursue him. Befriending Professor Kousaka's nephew and niece, Amazon learns of the GiGi Armlet's true nature and ultimately defeats Gedon, then the Garanda Empire.