With Gaoh having stolen the DenLiner and trapping the Imagins onboard, Ryotaro and Hana find themselves trapped in the year 2000 where they meet Ryotaro’s younger self, but Ryotaro is slowly forgetting everything having to do with Den-O! As Gaoh gets closer to his target, the only hope lies with Yuuto’s complex plans and a little bit of luck, or else time itself could fall victim to Gaoh’s evil desires!
With Kai’s defeat, Ryotaro and the rest of the DenLiner crew resume their time-traveling adventures by founding a detective agency to keep any other surviving Imagin in check. But when a rogue Imagin swipes Owner’s spare Den-O Pass, it’s up to the DenLiner Police and rookie detective Kazuya, along with a little help from another Rider, to stop the evil Imagin and save the past, present, and future!
Under the impression that they saved the World of Den-O, Tsukasa Kadoya (Kamen Rider Decade) and company begin their journey to the World of Kabuto when they are halted by Sieg who presents them a manuscript that detailed the legendary Oni Conquest with Momotaros' image on it. As this occurred, the Tarōs mysteriously vanish from the DenLiner as they are about to help Kotaro Nogami (Kamen Rider New Den‑O) out with the true threat to their world.
