Eiji Hino es un viajero que no tiene un hogar propio y que carga con un trágico pasado. Cuando despiertan después de 800 años unas criaturas hechas de unas extrañas medallas de metal llamadas Greeeds que se alimentan de los deseos y la codicia de los humanos, Eiji encuentra una de las medallas, perteneciente a Ankh, un Greeed del que solo queda un brazo flotante. En el primer ataque, un joven inspector de policía llamado Shingo Izumi al que Eiji acaba de conocer resulta gravemente herido y queda al borde de la muerte. Ankh, que entrega a Eiji un cinturón con el que se transforma en Kamen Rider OOO, aprovecha para poseer el cuerpo de Shingo antes de que este muera para poder andar libremente, teniendo como efecto secundario el conservar con vida al inspector mientras Ankh esté dentro de él. Junto a la hermana del inspector, Hina, y con la ayuda de Ankh que le proporcionará medallas para usar sus poderes, con la intención de recolectar las medallas de los Greeeds que destruyan para obtener más energía; y de la misteriosa fundación Kōgami que les proporciona equipamiento y tecnología a cambio de parte de las medallas que consigan, Kamen Rider OOO tendrá que enfrentarse a los Greeed antes de que recuperen todas sus medallas Core y se conviertan en una amenaza que podría consumir el mundo entero.
Episodios
1. Medallas, calzoncillos y una mano misteriosa
5 sept 2010 25m 9.0A 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.
2. Ambición, helado y un regalo
12 sept 2010 25m 10.0Ankh 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.
3. Episodio 3
19 sept 2010 25mAnkh 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.
4. Episodio 4
26 sept 2010 25mAnkh threatens to leave OOO for Kazari and the Greeed while investigating the evolution of humanity while Eiji tries to find more about Hina.
5. Episodio 5
3 oct 2010 25mKougami asks for a share of Eiji and Ankh's Medals, while Mezool decides to use Hina's shopaholic classmate to create a new Yummy.
6. Episodio 6
10 oct 2010 25mHina confronts Yamano's shopping addiction when her father goes bankrupt while Ankh confronts Kougami about his share deal of the Cell Medals.
7. Episodio 7
17 oct 2010 25mEiji 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.
8. Episodio 8
24 oct 2010 25mEiji gets to the root of the Komoris' problem involving greed and loss of ambition while Ankh fights for survival after a failed confrontation with Uva.
9. Episodio 9
31 oct 2010 25mA serial bomber tied to a nest of Yummies leads to Eiji to reveal his past to Hina and forces him to encounter a strange man he believes is Mezool's victim.
10. Episodio 10
14 nov 2010 25mEiji must figure the means of stopping the mad bomber and his Yummies to prevent any more lost lives, even with Maki observing the creation of his worker's monsters.
11. Episodio 11
21 nov 2010 25mEiji's traveler friend becomes manipulated by Uva into becoming famous as he steals others attributes; while Gotou doubts Eiji's effectiveness as OOO.
12. Episodio 12
28 nov 2010 25mEiji teaches a lesson to Tsukuba and Gotou about going forth to gain what is desired; while Ankh tries to figure a way to manage the flying Ageha Yummy using Gamel.
13. Episodio 13
5 dic 2010 25mAnkh is at a breaking point with everything surrounding his human host; a highly sought after doctor has been repeatedly removed from the operating room, making her frustration a perfect target for the Greeed.
14. Episodio 14
12 dic 2010 25mBoth Hina's brother and the hospital director are in critical condition after Ankh's detachment and the Yummy attack. Eiji must find both Ankh and the affected surgeon before it's too late.
15. Episodio 15
19 dic 2010 25mAnkh finds one of his core medals; Gotou is transporting a truck full of medals to Doctor Maki; Kazari appears to Ankh and Eiji, telling them that Hina is in Gotou's truck.
16. Episodio 16
26 dic 2010 25mEiji learns about how the Greeed were born; Gamel searches for Mezool; Kamen Rider Birth joins the fight.
17. Episodio 17
9 ene 2011 25mThe Greeed take an interest in a girl who wants to get better at kendo; Ankh takes an interest in Kamen Rider Birth; Hina gives both Eiji and Ankh gifts for saving her.
18. Episodio 18
16 ene 2011 25mEiji and Ankh try to find out the reason that the Yummy split in two, but Kamen Rider Birth is one step ahead of them.
19. Episodio 19
23 ene 2011 25mKougami tries to give Eiji one of Ankh's medals, but he refuses; a face from the detective's past shows up at Cous Coussier; thanks to Kazari, a criminal that the detective put away is on the streets and looking for revenge.
20. Episodio 20
30 ene 2011 25mAnkh tricks Kazari by telling him that Eiji knows where his last medal is and then chases after Hina who has his own medal; Date and Gotou discuss the skills need to be Kamen Rider Birth; Kougami changes his mind and sends Ankh's medal to Eiji.
21. Episodio 21
6 feb 2011 25mThe Cous Coussier gang runs into a young boy getting attacked for telling off a man for littering, learning that it's something he picked up from his father; the Greeed creates a Yummy from the desire to help people.
22. Episodio 22
13 feb 2011 25mSusumu lets his desire for justice get out of hand and it's up to Eiji to stop him before it's too late; Gotou and Takashi have a heart-to-heart conversation about their ideals.
23. Episodio 23
20 feb 2011 25mKazari is drawn to the vanity of woman whose sister takes all the credit for her work.
24. Episodio 24
27 feb 2011 25mEiji is head over heels for Yuumi and it's up to Date to save his old friend before she does something that she'll regret.
25. Episodio 25
6 mar 2011 25mAnkh is acting more standoffish than usual; a boxer is forced into retirement just before a big match and is captured by a bird Yummy.
26. Episodio 26
20 mar 2011 25mEiji is still super beat up from the previous battle but he is the only one who believes that Ankh did not create the bird Yummy; Kazuki heads back to the ring as Date and Gotou rush to stop him from injuring himself more.
27. Episodio 27
27 mar 2011 25mKougami invites Eiji and Ankh over to celebrate the 1000th episode of Kamen Rider and decides to make a movie to celebrate; Kazari is drawn to a Shocker grunt who joins the movie.
28. Episodio 28
3 abr 2011 25mEven though he's injured, Date still wants to finish directing the movie; Sendou starts sabotaging the movie with his new friends.
29. Episodio 29
10 abr 2011 25mKazari uses Dr. Maki's desire to make a Yummy; Gotou goes back to work; a strange monster shows up with Ankh's other arm.
30. Episodio 30
17 abr 2011 25mDr. Maki and Chiyoko have a heart-to-heart talk about his sister; Kazari takes Ankh's memoryless body under his wing; Kougami tells Gotou the story of the medals as Eiji and Date get Ankh to finally tell his story.
31. Episodio 31
24 abr 2011 25mDr. Maki and Kazari try to awaken a brand new Greeed; a man has been unknowingly using Greeed money to pay off an old debt; Eiji gets infected by purple core medals.
32. Episodio 32
1 may 2011 25mAn x-ray reveals that there should be nothing wrong with Eiji; Date tells the others about the time he previously ran into Eiji; Eiji uses the purple medals.
33. Episodio 33
8 may 2011 25mEiji is forced to use the purple medals again; an old friend from High School invites Eiji to an amusement park where Hina is then kidnapped; a Yummy abducts Date and Gotou.
34. Episodio 34
15 may 2011 25mAnkh tells Eiji about what his friend has been doing; a Yummy kidnaps Ankh; Eiji forces himself to use the purple medals.
35. Episodio 35
22 may 2011 25mHina wins first place in a fashion contest and is offered a chance to study in France; Dr. Maki creates a Yummy that destroys people's dreams; Date collapses in battle and Kougami finds an interesting x-ray on his brain.
36. Episodio 36
29 may 2011 25mHina's brother has woken up, leaving Ankh without a host; Eiji discovers Hina destroying all of her clothes after getting her dream broken; Uva revives Mezool and Gamel.
37. Episodio 37
5 jun 2011 25mGotou finds Date avoiding his checkup; a Yummy causes people all over the city to suffer from insomnia; Dr. Maki makes Date an offer.
38. Episodio 38
12 jun 2011 25mDate joins forces with the Greeed; Gotou tries to raise the 100 million yen himself; a new Birth is born.
39. Episodio 39
26 jun 2011 25mAnkh has nightmares about losing Eiji to the purple medals and other Ankh; a man has set up surveillance cameras all over the neighborhood, trying to force out Eiji and Ankh because they make the neighborhood look bad; now that Gotou is Birth, Kougami assigns Satonaka as Birth's new partner.
40. Episodio 40
3 jul 2011 25mThe Cous Coussier crew get thrown out of town where they decide to throw Ankh the birthday party for Hina's brother; the Yummy has holed himself up with a human barricade, forcing our heroes to wait until he surfaces again; the other Ankh waits for his other self to let his guard down so that he can become whole again.
41. Episodio 41
10 jul 2011 25mAnkh is absorbed into a single body, but the two halves are still not completely whole; Eiji begins to wonder about his place in the Izumi family's life as Shingo tries to help him out in Ankh's place; Gotou helps Eiji on his mission to rescue Ankh, but Eiji is stopped by Dr. Maki.
42. Episodio 42
17 jul 2011 25mDr. Maki explains to Eiji about the process of becoming a Greeed and the dulling of the human senses, leading Eiji to discover that it is already happening to him; a Yummy is trapping people in ice and calling out for OOO's help, but HIna refuses to let him go; Eiji does battle with Ankh, destroying.his core medals.
43. Episodio 43
24 jul 2011 25mAfter Ankh's cores were destroyed, he becomes in need of a body and yet again takes the detective's, also realizing that he's different now and creates a Yummy; Hina comes to the conclusion that she's been too selfish and reliant in regards to other people, making the decision to change and stand by Eiji no matter what; Ankh revives Uva and makes a deal with Dr. Maki to become his container of medals.
44. Episodio 44
31 jul 2011 25mKazari and Ankh butt heads over who is the leader of the Greeed; Hina and Gotou try to find Eiji's desire so that the purple medals will stop making him go berserk; Hina stops Ankh from taking medals from Eiji, but Kazari swoops in and gets the last of his nine medals; Eiji destroys one of Kazari's core medals, allowing Dr. Maki to steal the remaining medals from a weakened Kazari.
45. Episodio 45
7 ago 2011 25mWith Birth in need of repair, Erika retrieves the Prototype Birth driver in order to make do; because they are at a major disadvantage, Eiji and Gotou decide to go on the offense and attack the Greeed first; the other Greeed confront Dr. Maki and Ankh, with Mezool fully reviving and leaving Gamel, who also has the remainder of his medals.
46. Episodio 46
14 ago 2011 25mGamel rampages throughout the city trying to revive Mezool with one of her core medals; Eiji washes up on the beach with the purple medals acting up, and before he can find his driver, Ankh shows up to stop him from turning into a Greeed; Gotou has his Birth driver back, but he's in trouble and Erika gives the prototype to a familiar face.
47. Episodio 47
21 ago 2011 25mDr. Maki makes Eiji go berserk and fight Ankh when he won't give up the purple medals, but Ankh can't force himself to purposefully hurt Eiji; Ankh believes that one of his medals was broken by Dr. Maki and lets Hina know that her brother will be returned soon; Eiji discovers his true desire; Uva is fully revived.
48. Episodio 48
28 ago 2011 25mEiji receives a present from Kougami; Dr. Maki decides to make Uva the container for the core medals; Ankh returns to Eiji's side as they prepare for the final battle.