Momotaros is one of the main heroic Imagin in the series Kamen Rider Den-O, and one of the Taros. As Ryotaro Nogami's first Imagin ally, he allows him to use Den-O's Sword Form. Momotaros eventually becomes the representative of the Den-O series, becoming Den-O himself.
Among the hundreds of Imagin that arrived to the year 2007, Momotaros entered the body of Ryotaro Nogami but unable to set up a contact as he is forced to possess Ryotaro when he is attacked by Tetsuo. But after Ryotaro mentally restrains him, Momotaros learns that Ryotaro is a Singularity Point and helps him as Den-O to defeat the Bat Imagin. Admitting he does not remember their mission, Momotaros actually prefers fighting for his own whims. Though Ryotaro gives him his name rather than a desire to fulfill their contact, Momotaros eventually grew to respect the human as well as the other Imagin they are partnered with. In time, Momotaros begins to take his mission as member of the Den-Liner to protect time to heart.
In the Den-O series finale, due to Kintaros granting Ryotaro's unintentional wish for the Taros to stay by his side, Momotaros and the others are able to be present alongside Ryotaro for the final battle with Momotaros accepting Ryotaro's actual wish to fight with him to the very end. After the battle ended, with his existence assured, Momotaros was distant and silence over parting ways with Ryotaro, only to jump to the window at the last second to say goodbye to his friend while promising to meet again as the Den-Liner departs back into the timestream.
That promise is kept during the events of "Final Countdown" when Momotaros is stunned to be fighting Ryotaro while he's possessed by the Ghost Imagin, nearly getting himself killed to free his friend as they fight together against Shiro with Ryotaro's grandson aiding them. Later, he becomes a hot-blooded member of the Den-Liner Police that is formed to battle Negataros. Though Negataros was destroyed, Momotaros keeps the new group together as he sees being a cop as a cool thing.
Decade and Cho Den-O movies
When the recently de-aged Ryotaro leaves to investigate the Oni disturbance in the past, Momotaros loses his physical form and memory as he possesses Yusuke Onodera, allowing him the ability to transform into Den-O Sword Form. However, Momotaros finds himself being attacked by Daiki Kaito who wants Den-O's powers. But when he teamed up with Tsukasa Kadoya, Momotaros regains his memories and physical form while Kamen Rider Decade acquires the Den-O Kamen Ride, Final Form Ride and Final Attack Ride Cards.
Though Decade thought he solved the issues in the main rider continuity (Den-O's world), time was still awry as Momotaros gets sent to the past in the Oni War, which the Den-O team and Decade fight in to ensure that the Oni from years past are exterminated, as history says. Sometime later, the Den-Liner gang face Daiki again when he uses them to steal a treasure in the past.
Let's Go Kamen Riders
Momotaros and the crew of the DenLiner encounter Eiji Hino/Kamen Rider OOO and the Greeed Ankh. Unfortunately, Ankh unintentionally altered the timeline which enabled Shocker to utilize the Core Medal to create the Shocker Greeed which defeated the Double Riders and seemingly erased the legacy of the Kamen Riders from history. In 2011, after Kamen Rider New Den-O's attempt to repair the damage, he along with Kamen Rider OOO and M-Ankh awaited execution. However, it was revealed the Double Riders had their brainwashing removed by a Shocker scientist.
The Double Riders joined with New Den-O and OOO to fight Shocker's forces, but were eventually defeated. When the order was given to kill everyone, V3 suddenly appeared, asserting that there were more than four riders. V3 was soon followed by all the other revived riders that came after him, as even though Rider history was changed, the people's memories haven't changed.
After Teddy returned, Momotaros became Den-O and assumed Climax Form when Urataros, Kintaros, and Ryutaros asked to join in, doing so until all the riders joined up. After the riders were united, they faced off against Shocker's Great Leader. Ankh used Momotaros to create the Imagin Core Medal, which allowed OOO to assume Kamen Rider OOO Tamashii Combo and defeat the Great Leader, though he soon came back as the Rock Great Leader. Later, when joined by a force of extra riders, Den-O and all the other riders got on their motorcycles and performed the "All Rider Break", ramming into the Rock Great Leader and defeating it once and for all. After it was over, everyone went their separate ways and Momotaros returned to the DenLiner which embarked on its next destination. OOO, Den-O, All Riders: Let's Go Kamen Riders
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 Galleon 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. While getting their guests there, debating over whose side they are on, Momotaros said that he was the leader of the "Imagin Sentai" because he was the red. When the Sentai teams and the Kamen Riders battle the Shocker-Zangyack Alliance, Momotaros and the other Taros join the fray in their Den-O forms, fighting alongside the Gekirangers. Momotaros chided Urataros for flirting with Geki Yellow in the middle of the fight. Momotaros later joined with other Kamen Riders to fight Doktor G, they were all overpowered by his Kani Lazer form until he was defeated by Kamen Riders Decade, Blade, and Ryuki, with a little help from the Goseigers. Kamen Rider × Super Sentai: Super Hero Taisen
Super Hero Taisen Z
Den-O was part of a force of Rider and Sentai reinforcements led by Kamen Rider 1 and AkarengerIcon-crosswiki that came to assist the Riders and Sentai of recent years who were overwhelmed by the revived monster army of the Space Crime Syndicate MadouIcon-crosswiki. The combined forces of superheroes were able to turn the tide against the Madou army. They lined up and used their various finisher attacks to destroy the revived monsters.
After Demon King PsychoIcon-crosswiki was destroyed and the battle was finally over, Den-O appeared standing on a cliff with all the other heroes who appeared to help, to say goodbye to the heroes of recent years before taking their leave. Kamen Rider × Super Sentai × Space Sheriff: Super Hero Taisen Z
Kamen Rider Wizard
|“|| Eh? What are you talking about? Are you an idiot or
something? We didn't do what those kids wanted because of the rings. We were just protecting the weak.
| ~ Momotaros reveals to Amadum that the Kamen Riders don't
Den-O appears with all the Heisei Riders from Kuuga to Fourze, led by Decade, in a special two-parter after the finale, The Kamen Rider Rings and Neverending Story. As the Rider's powers were absorbed by Amadum, Kamen Rider Gaim arrives to help Wizard and the rest of the Riders. Just as Gaim finally overpovers Amadum and forces the Riders powers retuning to the Heisei Riders and perform the respective Rider Kick, Gaim and Wizard finallly deliver Amadum a final blow by performing Rider Double Slash, thus ending the evil wizard's ambition for good. As the Rider Rings vanished, Momotaros returns to the DenLiner
Kamen Rider Taisen
|“|| I have arrived! I'm the founding father of train
heroes! Ore Gattai!
|“|| However... Why the hell am i become the feets,
|~ Den-O, when he becomes displeased as a feet part|
Den-O was seen in the DenLiner battling the Kuliner, however he got himself defeated. Den-O would later return along with the defeated Riders as they battle the Badan Empire. While the ToQgers were having a difficult time of fighting Generalissimo of Badan, Kyoryu Red and Den-O would assist them, forming the mecha into ToQ-Oh Kyoryuzin feat. DenLiner, but he is displeased because Kyoryu Red takes over the upper body, knocking the DenLiner down to being the feet. After battling the Badan Empire, Hongo stated that their battle wasn't over as the Rider War continues. However the Showa Riders admit their defeat after seeing Gaim protecting a flower as they would congratulate the youn.
- His voice actor, Toshiko Seki, also played Duo Maxwell from Mobile Suit Gundam Wing.