- Title: Kamen Rider Decade : All Riders vs. Dai Shocker
- Alternative Title: 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
- Number of Episode: 1
- More Info: http://kamenrider.wikia.com/wiki/Kamen_Rider_Decade:_All_Riders_vs._Dai-Shocker
- Summary: The Hikari Studio arrives in a new A.R. World where, after seeing that Tsukasa's photos of this world are coming out perfectly, Natsumi realizes they may be in Tsukasa's home world. Tsukasa realizes he remembers the mansion depicted on the backdrop that took them here. Finding the manor, Tsukasa opens the door as he Natsumi and Yuusuke meet a girl named Sayo,who identifies Tsukasa as her older brother. As Sayo learns that Tsukasa lost his memories, revealing how he left her a year ago, her caretaker Nobuhiko Tsukikage arrives and confronts him about leaving his sister alone for so long. But when the Nine Worlds fusion starts to influence the World of Decade, Tsukikage reveals that Tsukasa's journey has now enabled a solution to the crisis by determining the strongest Kamen Rider in existence: The Rider Battle. When his memories return, Tsukasa gives Tsukikage the clearance to make it happen. Three days later, after numerous matches, it comes down to a 6-man tag team match between the team of Decade, Kuuga, and Diend vs. V3, BLACK, and Super-1. With Diend running off and Kuuga wounded, Decade is forced to defeat all three on his own. Upon victory, a castle emerges from the stadium with Yusuke and Natsumi finding themselves in the throne room surrounded by various monsters as they are welcomed to Dai-Shocker before Eijiro appears as he suddenly reveals himself to be Doctor Shinigami, toasting to their leader's return: Tsukasa. Revealing all of their actions were to ensure Dai-Shocker would achieve its goal of dominion of all the saved worlds, Tsukasa sends the horrified Natsumi and Yusuke into the sewers.
The two escape to the Kadoya mansion, learning of Tsukasa's childhood from Sayo before learning that she and Tsukikage are with Dai-Shocker as the latter becomes Shadow Moon while the former uses her Stone of the Earth on Yusuke, unleashing the greatest and most dangerous of Kuuga's powers within him. Yusuke tells Natsumi to run away before the powers are unleashed. At DaiShocker's castle, seeing the worlds still gathering, Tsukasa learns from Tsukikage that the Battle Fight was a farce as Sayo arrives, declaring herself High Priestess Bishium as Tsukikage reveals he outlived his purpose before dropping himself into the sewers, where he is attacked by Yusuke as Kuuga Rising Ultimate Form, under the control of Sayo. Tsukasa goes to the Hikari Studio to try to reconcile with Natsumi, who can no longer trust him for using her to achieve his ends. Tsukasa pleads with her as the Hikari Studio is now his only home, but Natsumi still refuses, as she is now alone in the world. The next day, Dai-Shocker begins its attack across the worlds starting with the World of Decade. Finding herself in the middle of it, Natsumi is saved by Narutaki into another conquered world before they run into Daiki who had disguised himself as one of the attacking Dai-Shocker Soldiers. Seeing hope in Daiki's ability to travel across worlds, Narutaki sees the only way to possibly save the worlds is to gather the Kamen Riders.
Elsewhere, with no one to turn to, Tsukasa is confronted by Jōji Yūki who attempts to get revenge on him for having lost his arm while working for Dai-Shocker. He is about to finish Tsukasa off until he realizes that Tsukasa has changed and that he is now Dai-Shocker's target. Yūki pulls off his arm, revealing its robotic replacement and allows Tsukasa to escape as he prepares his transformation into Riderman. Elsewhere, after an attempt to recruit Kamen Riders Ouja and Kick Hopper ends bad, Diend and Natsumi are attacked by a Dai-Shocker platoon under General Jark. Though he summons Raia, Gai, and Punch Hopper to distract their new enemies as he flees the area with Natsumi, Diend is cornered by Jark as Tsukasa arrives, now intent on fighting Dai-Shocker and saving his friends. With Diend's help, Decade drives off the monsters as Jark is destroyed by Diend.
Making their way to Dai-Shocker's castle, Natsumi and the two Kamen Riders are confronted by the entire Dai-Shocker army led by Doctor Shinigami and Ambassador Hell as Ikadevil and Garagaranda respectively. Things seem bleak until all of the other Riders arrive to help. After Garagaranda and Ikadevil are destroyed, the Bishium-controlled Rising Ultimate Kuuga arrives to kill Decade. Attempting to get to his sister, he convinces her that she can fly like him and realize that Tsukikage is only using her to further his goals. Sayo realizes the error of her ways, and destroys the Stone of the Earth, freeing Yusuke from its control as Shadow Moon decides to finish them off himself. Before Shadow Moon could move in for the kill after defeating Decade and Kuuga, the unexpected arrival of Kamen Rider Double (Shotaro Hidari & Phillip) tips the scales as he takes out Shadow Moon on their own before taking his leave, pinning Shadow Moon into the castle. All of the other Riders join Decade in an All Rider Kick, destroying Shadow Moon and the Dai-Shocker castle. The resulting shock awakens King Dark as Diend arrives with Kamen Rider J. Using the Decadriver Final FormRide card, he turns Decade into the Jumbo Decadriver which then turns J into Decade Complete Form Jumbo Formation and he destroys King Dark with a variation of the Dimension Kick, using the other Riders as giant Kamen Ride Cards. After parting ways with the Riders, and making amends with Sayo as she begins her own journey, Tsukasa begins his true journey within the Hikari Studio, his true home, where Eijiro reappears as if nothing had happened.