Kamen Rider OOO (仮面ライダーオーズ, Kamen Raidā Ōzu) is the primary and eponymous protagonist of the 2010-2011 Kamen Rider Series Kamen Rider OOO. The name "OOO" is pronounced similarly to both "O's", referring to the three O's in the television series' title which represent the character's transformation items, and "multiple kings" (王ｓ, Ōzu). The three O's also represent the infinity symbol with an additional circle, stating that Kamen Rider OOO is Over ∞ (infinity).

Kamen Rider OOO makes his debut appearance in Kamen Rider W Forever: A to Z/The Gaia Memories of Fate where he faces off against and defeats the Luna Dopant. An alternate spelling of the character's name is "Kamen Rider Ooz", which comes from Hyper Hobby magazine's September 2010 issue.

Eiji Hino

Eiji Hino (火野 映司, Hino Eiji, portrayed by Shu Watanabe) is the son of a politician who travels the world with his grandfather, thus growing up in a lavish environment. While in Africa a year prior to the beginning of the series, Eiji attempted to use his fortune to help out a small village. However, his money was used to fund a civil war that cost the life of a little girl Eiji befriended, whose death he was unable stop, forced to looked on helplessly. Though the Hino family used his sob story to get the people's support, the ordeal peculiarly caused Eiji to lose all selfish desires, resulting him being a vagabond with no permanent job, no home, almost penniless and no life. He became willing to help those in need, often going so far as to risk his life for complete strangers. Eiji's rationale for helping people is if someone reaches their hand out to him and he does not reach back, he will regret it for the rest of his life.

Kamen Rider OOO (仮面ライダーオーズ／ＯＯＯ, Kamen Raidā Ōzu) is a 2010-2011 Japanese tokusatsu drama in Toei Company's Kamen Rider Series, being the twelfth series in the Heisei period run and the twenty-first overall. It began airing on September 5, 2010, the week following the conclusion of Kamen Rider W, joining Tensou Sentai Goseiger and then Kaizoku Sentai Gokaiger in the Super Hero Time lineup, until its conclusion on August 28, 2011. The series' titular Kamen Rider made a cameo appearance in the film Kamen Rider W Forever: A to Z/The Gaia Memories of Fate.

Production

OOO is written by Yasuko Kobayashi, known for the screenplays of Seijuu Sentai Gingaman, Mirai Sentai Timeranger, Kamen Rider Ryuki, Den-O, and Samurai Sentai Shinkenger. The creature designers are Yutaka Izubuchi, known for his work on the Lords in Kamen Rider Agito, and Tamotsu Shinohara, known for his work on the Mirror Monsters of Ryuki, the Orphnoch of Kamen Rider 555, and the Fangires of Kamen Rider Kiva.

Unlike several previous Heisei Rider Series, no alternate name has been given yet for the three O's in the title (Ｗ（ダブル） read as "Double" and 555（ファイズ） read as "Φ's/Phi's/Faiz") aside from an alternate spelling of the name of the main Kamen Rider: Ooz. Both "OOO" and "Ooz" are intended to be read as "O's", referring to the multiple uses of the letter O in the title as well as "multiple kings" (王ｓ, Ōzu). The title OOO signifies the three medals that the main Kamen Rider uses to transform as well as being representative of the infinity symbol () with an additional circle.