Ryutaros (リュウタロス Ryūtarosu) is the fourth Imagin that gives Ryotaro Nogami the ability to assume Kamen Rider Den-O (仮面ライダー電王 Kamen Raidā Den'ō, lit. "Power King")'s Gun Form.
Promised by Kai that he would become the Den-Liner's conductor if he kills the Singularity Point, Ryutaros enters Ryotaro's body prior to his contact with Urataros. He is eventually revealed when Issē Miura places Ryotaro under hypnosis, able to force the other Taros out of Ryotaro as he takes the human's body for a spin. Later emerging from Ryotaro's body when attracted by Naomi's coffee inside the Den-Liner, revealing his intent to kill Ryotaro, Ryutaros is revealed to have a Rider Ticket Kai gave him that allows the Imagin to remain on the train. However, having developed feelings for Airi Nogami, Ryutaros decides to not go through with it. Because he knows that Airi has loved Yuto Sakurai, Ryutaros was jealous and took faulty advice on love from Kintaros to nearly kill Yuto in a fight before Ryotaro took control. Though he forgave him for previous moments, Ryotaro gives Ryutaros a severe warning not act on his own again. Ryutaros is also credited with being the one who allowed Sieg to come upon the Den-Liner, even allowing him access to a luxurious train car.
During the events of Kamen Rider Den-O: I'm Born!, Ryutaros possesses the Ryotaro that Yuto brought for the Climax Scene. This has a negative side effect which caused Ryutaros to fade from existence were it not for Ryotaro's feelings condensing his remains into the K-Taros, restoring him to normal while allowing Ryutaros to form the chest armor of Den-O's Climax Form until his synch with Ryotaro was negated. However, Ryutaros drew up the concept design of the DenKamen Sword, his power now accessed in the Ryu-Gun Mode.
Eventually, Ryutaros meets up with Kai,who tricks him into sabotaging the Zero-Liner without knowing the consequences of the Den-Liner being taken and rendered powerless. Due to the event, Ryutaros matures and takes the new timeline's effects hard, being forced to realize that he couldn't be with Airi as she recognized him not to be her Ryotaro. After Ryotaro stands up to Kai for him, Ryutaros, like the other imagin, learns repect towards Ryotaro and is now more willing to help Ryotaro out in any way he can. Ryutaros can perform his own variation of Gun Form's finisher, Wild Shot, although it is simply a powered shot due to the lack of additional charges.
As the new year approaches, Ryutaros is saddened and confused over both Kintaros's and Urataros's decision to abandon the Den-Liner and remain in the past to fend off the Imagin army. During the final battle, he catches Ryotaro as he falls from a building at the last second, and is the first to fight the Death Imagin as Den-O Gun Form, and lent his power for the finishing blow against the Death Imagin. During the events of Climax Deka, as a member of the Den-Liner Police, Ryutaros causes an incident while searching for the "Evil Organization", arresting anyone who merely looked suspicious. He finally gets his closure with Airi when they meet face to face and he bashfully accepts the meal she made. During the events of "Final Countdown", Ryutaros assumes Gun Form (on his own) during the epic battle against the revived Imagin, determined to protect the time from being destroyed, having seen an Airi doppelganger in the time where they were, who also turns out to be an ancestor of Ryotaro and Kotaro.
Super Hero Taisen
Momotaros discovered Daiki holding up the stolen cup of Den-Liner Purine pudding that he stole from him during their last meeting. The Den-Liner rendezvoused with the Gokai GalleonIcon-crosswiki where Daiki was standing with Hina Izumi and Gokaigers Joe Gibken and Don Dogoier to get back the pudding. Picking up the four passengers, the Den-Liner took them to Winter 1976 to pick up Akarenger. When the Sentai teams and the Kamen Riders battle the Shocker-Zangyack Alliance, the four Taros join the fray in their Den-O forms, fighting alongside the GekirangersIcon-crosswiki.
Kamen Rider Taisen
The DenLiner, piloted by Momotaros, is attacked by a KulinerIcon-crosswiki sent by General SchwarzIcon-crosswiki of the Shadow LineIcon-crosswiki as they join forces with the Underground Empire Badan, resulting in the time train's destruction with Momotaros being turned into the Den-O Lockseed. However, the DenLiner returns with Momotaros when the Riders are restored. With the DenLiner Gouka combining with ToQ-OhIcon-crosswiki, the other Taros participate in their Liners with ZeroLiner in the finishing attack of ToQ-Oh Kyoryuzin feat. DenLinerIcon-crosswiki, Fumikiriken Brave Sanjou Slash, which is used to destroy the Generalissimo of Badan. Heisei Rider vs. Showa Rider: Kamen Rider Taisen feat. Super Sentai
Despite not appearing on-screen (his voice actor was present in the movie, but voicing other characters), Ryutaros/Den-O Gun Form's participation in the final battle is indicated by the appearance of DenLiner Ikazuchi in the finishing attack.