Daisuke Yamamoto was an infant around the time of the plane he and his family were on crashed in the Amazon rainforest, leaving young Daisuke the sole survivor and grew up as a wild child, living off the land under the name of "Amazon. However, Daisuke'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 Daisuke for safekeeping while using his knowledge of Incan science and magic to perform a mystical "operation" on Daisuke, 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, Daisuke could not speak coherent Japanese and say only a few words. But through Masahiko helping him cope with the culture shock, Daisuke learned to speak properly.
 Fictional character biography
Under Bago's instructions, Daisuke evades Gorgos and his minions and makes his way to Tsubata, Ishikawa in Japan where he meets Professor Kōsaka, who knew the nature of the Gigi Armlet. Meeting Kōsaka's nephew Masahiko, who obliges to teach him to speak and the ways of the world, Daisuke is infuriated at Kōsaka being murdered by the Kumo Beastman and drives him off to save Masahiko and his sister Ritsuko, who blamed him at first for her uncle's death until he made an antidote to the poison her friend Masako got from the Beastman Vampire Koumori.
While catching fish, Daisuke finds himself at a motocross, frighted by the culture shock before he saves a man named Tōbei Tachibana who was attacked by Kamakiri Beastman. Paying him back, Tōbei helps Daisuke overcome his fear of motorcycles to save Masahiko from the Akajuusha before Kamakiri attacks them, with Amazon killing the Beastman. But unerved why he is hunted by the Geddon, Masahiko learns of Yamamura, one of the members of Kōsaka's exploration party into the Amazon. Hoping to find the answer, they and Tōbei learn that Yamamura's on the run from Geddon as he holds the secret that Geddon would go to lengths to make silent. When the Beastman Omukade captures Yamamura and his daughter, Daisuke pursues with newly built Jungler, saving them before killing the Beastman Omukade. During the fight, Yamamura is fatally wounded by the Akajusha as Yanamura reveals the "GaGa Armlet", the counterpart of the GiGi, that Gorgos possesses before he died.
During the Mogura Beastman incident, Daisuke is arrested by the police for attacking an officer when they needed to know his identity in spite of his part in helping them get murderer Oshima. Though bailed by Tōbei, a confused Daisuke runs off with a hatred for humans. The next day, Tōbei and Ritsuko find Daisuke as he intends to return to the Amazon. Learning that Masahiko was abducted by Mogura and at Ritsuko's pleas, Daisuke saves his friend and give Mogura a severe beating. Daisuke later finds Mogura being punished for failing Gorgos, saving the Beastman who is shocked. Later, after being told by that Johoku University has gain relics from the Amazon that might shed some light, Daisuke and friends investigate and find the mysterious Quipu which Daisuke could deciefer. But the Beastman Yamaarashi arrives and steals the Keep with Daisuke falling into his trap. But with Mogura's aid, Daisuke learns the story behind the GiGi and GaGa Armlets before killing Yamarashi, now knowing Geddon's goals.
While searching for Geddon, Daisuke receives a radio from Masahiko so he can know when Gedon's up to no good. After saving a woman from Kani Beastman, Daisuke learns that Mogura is forced by the monster of reveal Ritsuko as a potential weakness. Though he attempts to protect Ritsuko, Daisuke is saddeded as she tells him that he's the one Geddon's after and it might be best for everyone if he just goes back where he came from. In spite of this, Amazon saves Ritsuko and friend from Kani and later receives a vest from Ritsuko as her way of thanking him. As Daisuke manages to learn to speak and understand perfect Japanese, he attempts to find Geddon's safe house in order to take the GaGa Armlet from Gorgos. But he is unaware of the Garanda Empire who offer the Geddon Beastman Hebitonbo a place in their group if he get the GaGa Armlet for them. Hebitonbo enlists Amazon's aid in fight Gorgos before attempting to take the GiGi Armlet as well. But the fight ends with both Hebitonbo and Gorgos dead as the GaGa Armlet then falls into the hands of the ruthless Great Emperor Zero.
Learning of Garanda's extistece form the Hachi Beastman incident, Amazon fights against the new evil with Mogura's aide before he died helping him against Kinoko Beastman. As Garanda sets up its final plan, the Helium Bomb Operation, Sanshouo Beastman is sent to kidnap the Okmura siblings to hold off Amazon while the plan is completed. However, Amazon manages to defeat Sanshouo before following the Beastman's blood to Garanda's base and braves the traps waiting for him before facing Great Emperor Zero himself who negates the Gigi Armlet as the Kamen Rider is captured. However, Tōbei poses as a Kurojuusha to find Amazon as Zero is about to execute him. But freed when the Gaga Armlet combines with the Gigi Armlet, Amazon becomes immune to Zero's power as he chases after him before the Garanda leader falls into one of his traps. Destroying the detonation system for the Helium Bomb, Amazon confronts the real Emperor Zero and kills him. With his mission complete, he returns to the amazon forest where he lived because it is his true home, though Tōbei believes that he will come back if evil comes to terrorize Japan again.