Kamen Rider OOO was a 2010-2011 entry into the Kamen Rider Series, being the twelfth series in the Heisei period run and the twenty-first overall. It began airing on September 5th 2010 until August 28th 2011 (48 episodes). The series’ titular Kamen Rider made a cameo appearance in the film Kamen Rider W Forever: A to Z/The Gaia Memories of Fate.
Eiji Hino is a traveling man 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 Greed named Ankh gives Eiji a belt and three Medals to fight the other Greed as Kamen Rider OOO. The mysterious Kougami Foundation approaches Eiji and begins assisting him in his fight against the Greed, though their true motives are not clear. As Eiji fights the Greed and their Yummy monsters, learning more of the Greed and Ankh, he starts to find a purpose beyond his journey.