Eiji Hino is a wanderer who has no place to call home and a tragic past. When metallic creatures known as the Greeed awaken after their 800-year slumber to attack humans and feed off of their desires, the disembodied arm of the Greeed named Ankh gives Eiji a belt and three Medals to fight the other Greeed as Kamen Rider OOO. The mysterious Kougami Foundation approaches Eiji and begins assisting him in his fight against the Greeed, though their true motives are not clear. As Eiji fights the Greeed and their Yummy monsters, learning more about the Greeed and Ankh, he starts to find a purpose beyond his journey.
Episode 1
A mysterious arm reawakens the Greeed from their slumber and decides to use Eiji Hino, a cheerful wanderer, as his means of getting back what he desires as Kamen Rider OOO.
Episode 2
Ankh explains the Greeed and the purpose of the Medals to Eiji, even as the human desires to merely use his new power to fight for good instead of for selfish needs.
Episode 3
Ankh becomes troubled when Eiji prevents him from eliminating his possessed body's sister while another Greeed uses a man's gluttony to create more Medals.
Episode 4
Ankh threatens to leave OOO for Kazari and the Greeed while investigating the evolution of humanity while Eiji tries to find more about Hina.
Episode 5
Kougami asks for a share of Eiji and Ankh's Medals, while Mezool decides to use Hina's shopaholic classmate to create a new Yummy.
Episode 6
Hina confronts Yamano's shopping addiction when her father goes bankrupt while Ankh confronts Kougami about his share deal of the Cell Medals.
Episode 7
Eiji tries to research a husband bullied by his wife that is being mocked by Gamel while Ankh follows a lead for a missing Core Medal.
Episode 8
Amidst Hino's failed attempts at stopping the Komoris' argument, Momoko takes the winning scratchcard and throws it into a nearby river. As Takeshi frantically searches for it, she reveals to Hino why Takeshi has become so greedy.
Episode 9
In flashbacks, Eiji fails to save a girl amidst a foreign civil war. In the present, Satonaka meets with Eiji to collect Kougami's fee until an explosion occurs outside.
Episode 10
As Maki observes the bomber, Kougami Biotech Laboratory technician Toru Tadano, Ankh scolds Eiji, who later discovers Maki's whereabouts.
Episode 11
Eiji encounters an old friend and globetrotting blogger, Keisuke Tsukuba, who has come to Japan to find a publisher for his work.
Episode 12
Following Goto's attack, the Ageha Yummy retreats again while Eiji learns of Goto's distate towards him.
Episode 13
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Episode 14
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Episode 15
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Episode 16
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Episode 17
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Episode 18
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Episode 19
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Episode 20
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Episode 21
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Episode 22
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Episode 23
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Episode 24
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Episode 25
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Episode 26
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Episode 27
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Episode 28
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Episode 29
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Episode 30
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Episode 31
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Episode 32
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Episode 33
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Episode 34
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Episode 35
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Episode 36
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Episode 37
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Episode 38
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Episode 39
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Episode 40
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Episode 41
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Episode 42
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Episode 43
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Episode 44
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Episode 45
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Episode 46
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Episode 47
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Episode 48
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