Nine universes of the previous Kamen Riders from the Heisei era are merging into one, something that would destroy all the worlds. To prevent this, Tsukasa Kadoya transforms into Kamen Rider Decade and is told that to protect his own world he must travel to all of the other Kamen Riders' worlds (Another Rider's worlds) and eliminate the anomalies in those worlds. Along the way, confronting the mysterious Narutaki and the thief Daiki Kaito, they are joined by Yusuke Onodera of the World of Kuuga and Kivala of the World of Kiva.

Masahiro Inoueas Tsukasa Kadoya / Kamen Rider Decade
Ryouta Muraias Yusuke Onodera / Kamen Rider (A.R.) Kuuga
Kimito Totanias Daiki Kaitou / Kamen Rider Diend
Kanna Morias Natsumi Hikari
Tori Matsuzakaas Takeru Shiba / Shinken Red
Hiroki Aibaas Ryunosuke Ikenami / Shinken Blue
Rin Takanashias Mako Shiraishi / Shinken Pink
Shôgo Suzukias Chiaki Tani / Shinken Green
Suzuka Moritaas Kotoha Hanaori / Shinken Yellow
Keisuke Sohmaas Genta Umemori / Shinken Gold
Toshiki Inoue
Yasuko Kobayashi
Kenji Konuta