"You count the Medals, one, two, and three! Life goes on, anything goes, coming up OOO!"
Kamen Rider OOO (pronounced O's) is the story of Eiji Hino, a wanderer who owns nothing more than the clothes on his back and believes that all you need is a good pair of underwear to make it through your days. That all changes when strange monsters born of desire known as the Greed awaken. Their resurrection incomplete, they prey on humans, using them to create Yummies, monstrous embodiments of the victims desire, to generate the Cell Medals they need to survive while searching for the Core Medals that can restore them to their full power. One of them, Ankh, mysteriously only revived as his right arm and thus decides to grant Eiji the power of the OOO belt so that he can overpower and dominate his fellow Greed. All the while, the mysterious Kougami Foundation seeks to manipulate the course of this battle for its own purpose, for good or for evil.
Normally I try to review each series in its own terms, without references or comparisons to other entries in the franchise, but OOO is different; there are multiple, deliberate parallels to Kamen Rider Kuuga, and the awareness of these parallels and what they mean for the show are not something I can ignore or separate from my assessment of it. So let's get to it and get it out of the way.
In both Kuuga and OOO, the protagonist is a wanderer who's only tied down by his rider duties, and lives to enrich the lives of others with no concern or worry for their own well being. In Kuuga, he is a messianic figure, but in OOO, he is shell shocked and empty on the inside with stress placed on how damaging his behavior is for him. In both shows, the belt was originally used by an ancient warrior to seal away the monsters for that series, but while Kuuga's warrior was a hero who gave it his all for the sake of humanity's future, OOO's warrior was an insane tyrant who created the Greed as part of his (failed) plan to become a God. These are just two examples, but there are many more to be found in the show itself, and I wouldn't be surprised if I missed a few. The overall point is that OOO on the whole takes story elements from Kuuga and twists them on their head, either in their implications (a deconstruction) or in their premise (a subversion).
On the whole, OOO has a strong cast with each character having a strong sense of their goals, their "desires" if you will, and the conflict that emerges flows naturally. Notably, the conflict between Eiji and Ankh is handled really well due to the fact that at any given moment they both know exactly where they stand with one another and despite Eiji's unassuming manner and demeanor he frequently demonstrates a cunning and deviousness that makes him a match to Ankh's machinations. Thus we avoid the tedious and tired scenario conflict through the withholding of information, and instead get the flourish that comes from knowledge. The guests of the week who are used by the Greed to spawn Yummies are used to illuminate aspects of the main cast, and they do so quite well. The story is also strong, though its also making a fair few things up as it goes along, and while it does it well, that style of storytelling can be offputting.
On the downside though, much of the comedy is overt and wacky, and while I do enjoy it, it can break the mood. Furthermore, the OOO suit is, in my estimation, ugly. This is not just a matter of aesthetics, but also of how the suit functions; each time Eiji activates the suit, he inserts three medals, coressponding to his head, torso, and legs. Each medal is supposed to manifest a unique power, but a lot of the time the medals don't do anything in particular, not usually. It's too much clutter and noise to really work.
On the whole, I do think its a good series, but as I mentioned above, you really need to watch Kuuga first in order to appreciate the narrative choices made by OOO.