He is a young man with a lot of bad luck. When he first appeared, he managed to lodge himself in a tall tree while on his bike after losing control and going up a fallen sign. He has even placed a name tag in his wallet so it can be returned to him when it is stolen. Despite his hardships, Ryotaro will help anyone in need if he has the ability to do so. He refuses to accept self-sacrifice as the only means to protect others.
As a Singularity Point, he can resist the control of an Imagin contracted to him, among other things, as long as he's conscious. Due to this unique attribute, he was given the power to become Kamen Rider Den-O (仮面ライダー電王 Kamen Raidā Den'ō, Masked Rider Den-O), a Rider who protects the timeline from the Imagins' actions. As Ryotaro continues on his mission, he meets more Imagin, each taking his body and using it as their own for the duration of their possession. Each of his personality changes affect the color of his eyes and some strands of his hair, changing its color to match the Imagin while gaining their abilities and some of their strength along with it.
- When possessed by Momotaros, Momo is in Ryo's body. His hair spikes up slightly with a single red streak and he gains more muscular definition and the physical strength to go with it.
- When possessed by Urataros, Ura is in Ryo's body with the right words to woo women and convince almost anybody. His hair is straight and calm and has a single blue streak going through it. He also wears a pair of black rimmed eyeglasses.
- When possessed by Kintaros, Kin is in Ryo's body. His hair grows such that he has a ponytail with a golden yellow streak through it. However, his increased strength often results in self-injury and clumsiness.
- When possessed by Ryutaros, Ryu is in Ryo's body, incorporating dancing into everything he does. He grows one long purple and black streak of hair and is always seen wearing a brown cap. His reckless personality infests itself upon Ryotaro, and usually causes him to destroy whatever is around if he gets out of control. One such incident occurred during the events of Climax Deka when R-Ryotaro arrested everyone who he thought looked suspicious and was part of the "Evil Organization" advertised by Negataros.
- When possessed by Sieg, though they never forged a contract, Sieg is in Ryo's body. His hair is styled in cornrows and has several white highlights with one longer white and black lock on the left side of his face, and a white feather boa appears around his neck.
- While Yuto was removed from time, Ryotaro gained a contract with Deneb, Deneb is in Ryo's body. His hair grows out past shoulder length with two locks of hair on each side of his head. On the right side, the lock is a neon green with a darker green streak within it.
A shy and rather timid man, Ryotaro was originally very weak willed. His weak will made him only be able to use Plat Form at first. Even though Ryotaro was weak willed, he was kind and friendly from the start as he helped others as Den-O as well as saved Kintaros from disappearing. He is also quite honest as he was very displeased at Momotaros when he tried stealing money. It was also shown in the same episode that he is very stubborn as he refused help from Momotaros until he apologized, despite nearly dying in the situation for his lack of power. He also saw through Urataros`s reason for lying at Hana was to convince Daiki to tell the truth hinting an intelligent side. He can be quite stern when necessary as he scolded Ryutaros when he nearly killed Yuto out of jealousy. He also did it understandingly though, as he knew Ryutaros didn't do it out of malice. Ryotaro often tries to see the good in people despite how they initially appear to be, earning him the Taros`s friendship and loyalty which he returned fully. As mentioned before, Ryotaro was originally weak willed, and could only access Plat form without the influence of Momotaros and the others. It was after he became more strong willed as Den-O and being with the Taros did he gain access to Liner Form by himself showing how much willpower he gained through the course of the series. Oddly enough, Ryotaro seems to have changed and acted more bold when he became younger.
Kamen Rider X
Kamen Rider Amazon
Kamen Rider Super-1
Kamen Rider ZX
Kamen Rider Black/RX
Kamen Rider Kuuga