The staff of the Kamen Rider Zi-O, the latest installment in the Kamen Rider franchise, announced on Sunday that Toshiki Kashu, Rina Akiyama, and Akiyoshi Shibata will appear in the series. They will reprise their roles from the 2001 Kamen Rider Agito series as Shoichi Tsugami/Kamen Rider Agito, Mana Kazaya, and Takahiro Omuro, respectively. The characters will appear in the show's 31st and 32nd episodes on April 14 and 21, respectively.
The story of the episodes featuring the characters begins at a test site, where Omuro is demonstrating two G3 Units to the police top brass in an effort to deploy them nationwide. The site is suddenly attacked by "Another Agito" (the Kamen Rider Zi-O series features "Another Riders," evil versions of protagonists from Heisei Kamen Rider series).
The new Kamen Rider Zi-O series premiered last September and is based on a time-traveling theme (the series' "Zi-O" title alludes to jiō, literally "lord of time"). The titular hero wears the RideWatch and ZikuDriver items that allow him to transform. The new Kamen Rider Zi-O's power allows him to wear the suits of all the Heisei-era Kamen Riders and gain their power.
The story centers around a boy born in the year 2000, who has dreams of becoming a king. In the fall of 2018, the boy meets a girl who appears before him in a time machine. The girl explains that she comes from the future year of 2068, a hopeless future where a demon king rules and people suffer. The girl further explains to the boy that his destiny will be to become "Zi-O," the same demon king that will rule over the world.
Source: The Mainichi Shimbun's Mantan Web