Kamen Rider Den-O

"“I have arrived!” (俺… 参上！ Ore… sanjou!) —Momotaros as Kamen Rider Den-O"Kamen Rider Den-O (仮面ライダー電王 Kamen Raidā Den'ō, Masked Rider Den-O) is the main protagonist of same series.

Profile
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.

Story
The son of Shinichi and Kayoko Nogami, Ryotaro lost his parents while in childhood with his older sister Airi caring for him along with their grandmother, making visits to the closed down Milk Dipper that his parents owned. He kept the only picture of their parents with them until he lost it, feeling regretful of it since. He and Airi eventually re-opened the Milk Dipper with the aid of his sister's fiancé. However, when Airi's fiancé mysteriously disappeared a month before the wedding, resulting in Airi's current amnesia of everything related to the man, Ryotaro dropped out of high school to help his sister at the Milk Dipper, being burdened that his sister made herself forget about the fiancé and attempts to make sure she is not reminded and be hurt.

When he finds the Rider Pass, he unwittingly becomes the protector of time and space known as Kamen Rider Den-O, fighting the Imagin who traveled to the year 2007 to grant wishes and travel further into the past to change the future to their liking. As he is a Singularity Point, he is immune to the effects of changes to the past, and he can also resist the temptations of an Imagin, as seen with the hotheaded Imagin he named Momotaros, whose contract provides Den-O with a fighting form. He is assisted by the Singularity Point Hana as well as the crew of the Den-Liner, a train that allows him to traverse time in pursuit of Imagin. They are the mysterious Owner of the Den-Liner and the dining car's waitress Naomi. Along the way, he becomes contracted to other Imagin who give him the ability to access three of Den-O's other forms. They are the lying Casanova Urataros, the herculean and narcoleptic Kintaros, and the childish yet strong Ryutaros.

Ryotaro later identifies a mysterious man who has been following him through the past as his sister's fiancé Yuto Sakurai, but then meets a young man who calls himself Yuto Sakurai and his Imagin contract Deneb, the team that can become Kamen Rider Zeronos. Upon meeting Yuto, he begins to learn more about the nature of time and the Imagin, and is told by Yuto that protecting people is not as important as protecting time. Ryotaro does not believe this and feels that the two are one in the same, and he will do so, despite his own weaknesses.

Ryotaro also briefly meets the Swan Imagin Sieg who allows him to access another form, and later the evil Kamen Rider Gaoh who hijacks the Den-Liner to travel to the past to obtain the the Gaoh-Liner, leaving Ryotaro without memory of being Den-O for a while, meeting his past self as a result, until Gaoh takes him to the Tokyo of December 26, 1988, the day Ryotaro Nogami was born, in an attempt to erase him. To defeat him, Yuto travels in time to pick up three other incarnations of Ryotaro for Urataros, Kintaros, and Ryutaros to possess and aid Ryotaro in the "Climax Scene", destroying the GaohLiner and defeating Gaoh. In the process, while getting to see his parents firsthand, Ryotaro learns how "people's memories are time".

Upon his return to the present, Ryotaro learns that because he retains only the memories of fighting Gaoh as Sword Form while his past selves are incapacitated, he has no memory of fighting as Rod, Ax, or Gun Forms. This causes Urataros, Kintaros, and Ryutaros to all dissolve into sand, from which Ryotaro's feelings manifest the Climax Cellphone K-Taros. This restores the three lost Imagin, and gives Ryotaro access to the stronger Den-O Climax Form.

When Ryotaro's actions cause the Junction Point to manifest, his sync with the Tarōs starts to dissolve as a side effect, forcing him to fight as Plat Form. However, solving the crisis in advance, the Tarōs use their powers to create the DenKamen Sword so Ryotaro can assume the powerful Den-O Liner Form so he can fight on his own. Shortly thereafter, he meets the Singularity Point Kai, who seeks to make the Imagin's future the true future, by seeking to destroy the Junction Point, who is later found to be Ryotaro's sister Airi. As a result, Ryotaro falls into a trap set up by Kai to keep him from Airi, with Kintaros and Urataros sacrificing themselves so Ryotaro can return to the present. In the process, Ryotaro learns that his missing memory is tied to the true identity of the one who will ensure that the flow of time and space leads to the future without Imagin: his niece who is revealed to be Hana/Kohana.

After the final battle is over, Ryotaro is saddened by the supposed loss of the Tarōs, only to find out that they and Sieg, still existing due to their memories together, are hiding in a ditch attempting to surprise him. Ryotaro is overjoyed that they are all still alive and celebrates happily. With his mission to protect time from Kai and his Imagin finished, Ryotaro relinquishes his Rider Pass back to the Owner of the Den-Liner, thanking everyone for what they have done for him. As he rides his bike back to the Milk Dipper, he is greeted by all of the riders of both the Zero-Liner and the Den-Liner who bid him a final farewell before departing into the time stream. Ryotaro smiles as they pass by, knowing that he will meet them again someday in the future.

Later, when an Imagin named Negataros steals the Rider Pass from Owner, Ryotaro joins the newly formed Den-Liner Police to stop Negataros and his "Evil Organization", succeeding thanks to the aid of Kamen Rider Kiva. After the case was closed, Ryotaro and the Den-Liner crew keep the Den-Liner Police going just for kicks.

However, Ryotaro is forced to resume being Den-O when he is possessed by the Ghost Imagin for Shiro, using the Signality Point in order to travel into the past while having the possessed Ryotaro as his enforcer, Kamen Rider Yuuki Skull Form. But through Momotaros' aid, Ryotaro manages to regain control so he can let his Imagin partner in his body to purge the Ghost Imagin before they finish the Imagin off in Climax Form. But during the climatic final battle against the revived Imagin, Ryotaro, Momotaros, and Kotaro assume their rider forms to defeat Shiro when he becomes Yuuki Hijack Form.

After formally meeting his grandson, Ryotaro promises him he won't divulge any learned knowledge of the future as he takes Kotaro and Teddy home on the Den-Liner.

Decade
With Ryotaro off investigating an error in the timeline, there is no one person with the Tarōs that has the power of Den-O and the Tarōs manage without a permanent body to use. Following the departure of Ryotaro, prior to Tsukasa and company entering Den-O's World), the Tarōs suddenly lost the ability to maintain their physical forms due to the actions of an unknown force that is altering their present at some time in the past. The alteration of the present also ended up de-aging Ryotaro a few years, making him a young boy/teenager as a result.

Seeing the Mole Imagin surfacing to be connected to it, Momotaros possesses Tsukasa to fight one. After being evicted from Tsukasa's body by Natsumi's pressure point, Momotaros attempts to re-possess Tsukasa, but ends up in the body of Yusuke instead. After Tsukasa manages to get Momotaros to talk back at the Hikari Photo Studio, M-Yusuke storms off to solve the mystery behind his world's crisis.

As he is trying to figure out why buildings are disappearing, M-Yusuke is confronted by Daiki who wishes to know where the DenLiner is, revealing a DenLiner Final FormRide Card in his possession that would supposedly allow Momotaros to regain his physical form. Momotaros refuses, and then begins a fight with Diend as Den-O Sword Form, escalating against him with Diend using Sasword and Saga to outnumber him before he is sent plummeting off of a building. He survives as Diend takes his leave for Momotaros to reconsider.

Elsewhere, as Tsukasa and Natsumi investigate Den-O's World by finding the DenLiner and use it to go back to the time it started, Urataros, Kintaros, and Ryutaros each possess Tsukasa, revealing that they were warned of Decade and believe he is connected to the disturbances in their world. When Tsukasa manages to force them all out, they take over Natsumi's body, each using her to fight Decade in their respective Den-O Form as Decade counters as Agito. During the fight, both Riders are transported to another dimension similar to where the Rider War took place in Natsumi's dream. The fight would ultimately end in a stalemate as the DenLiner picks them up. Upon entering, they are greeted by Naomi, Kohana, and Owner, who would talk to them about teaming up to solve the mystery.

After tending to his injuries from taking out another Mole Imagin, M-Yusuke is confronted by Tsukasa before he senses the Imagin he's looking for, the Alligator Imagin. Chasing him to the past, Den-O is nearly killed by the Alligator Imagin when Decade and Diend intervene, with Diend using his Riotrooper card to hold the Imagin at bay. Diend would once again offer Momotaros a true body of his own, but Decade somewhat defends Momotaros, regaining his access to Den-O's powers.

Through the modified Final Form Ride Card, Momotaros regains his physical form and, after a slight misunderstanding from Yusuke, takes out the Alligator Imagin by using Kuuga Gouram as part of his Finishing Attack. Although the crisis is over another occurs after Momotaros returns to the DenLiner, with the Tarōs disappearing and Momotaros ending up on Onigashima as part of the Oni Conquest legend.

Crossover Appearance
Project X Zone 3: War of Infinite Worlds

Kamen Rider Den-O appears as a Solo Unit, with different forms (Sword, Rod, Ax, Gun and Climax Forms) corresponding to the player's Attack Threshold.

Chou Super Robot Wars

Den-O operates his DenLiner, one of the auxiliary vessels in both versions of the game (Æ and M).

Cross Maximum 2: Exceed Sky

Den-O (including Sword, Rod, Ax, Gun and Wing Form) appears as one of the characters from Kamen Rider side along with some other Kamen Riders.