The story revolves around the nine previous universes of the Heisei Kamen Riders 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 with Natsumi and her grandfather to the other Kamen Riders' Worlds (referred to as an A.R. World or Another Rider's World) and eliminate the anomaly in that world. Along the way, confronting the mysterious Narutaki and the thief Daiki Kaito, they are joined by Yuusuke Onodera of the World of Kuuga and Kivala of the World of Kiva.
The Rider Army (ライダー軍, Raidā Gun?), first revealed in Natsumi Hikari's dream, composed of many Kamen Riders, all of whom where seemingly defeated by Kamen Rider Decade. However, Kamen Rider Kuuga survived the initial battle, assuming Ultimate Form to confront Decade once again with the two seemingly destroying each other in the ensuing battle. As Narutaki explains to Natsumi, the dream is a predestined event in which Decade will destroy all the worlds.
- Main article: List of Kamen Rider Decade characters
As the story of Kamen Rider Decade takes place amongst many different dimensions, the characters and settings change as the series go on. The only constant characters are Tsukasa Kadoya and the Hikari family: Natsumi Hikari and her grandfather, Eijiro. However, the group is joined by various members of the A.R. Worlds that they visit.
- Main article: List of Kamen Rider Decade episodes
All Riders vs. Great ShockerEdit
- Main article: Kamen Rider Decade: All Riders vs. Great Shocker
The film Kamen Rider Decade The Movie: All Riders vs. Great Shocker (劇場版 仮面ライダーディケイド オールライダー対大ショッカー, Gekijōban Kamen Raidā Dikeido: Ōru Raidā tai Daishokkā?) is to open in Japanese theaters on August 8, 2009, double-booked with the Shinkenger film. The film will feature a total of 28 Kamen Riders: the original 10 Showa Riders, BLACK, BLACK RX, Shin, ZO, J, the previous 9 Heisei Riders, Decade, and Diend. It will also feature the first on-screen appearance of the 11th Heisei Kamen Rider: Kamen Rider Double. The film also provides light to Tsukasa's memories due to Decade's relation with the mysterious Great Shocker organization, whose membership is composed of the various villians and monsters that previous Kamen Riders battled with.