Kamen Rider Decade: All Riders vs. Dai-Shocker

Tsukasa Kadoya is revealed to be the true leader of Dai-Shocker, a multiversal organization that has been manipulating events across the Nine Worlds. Though he lost his memories, he originally established Dai-Shocker with Tsukikage and Sayo to protect the worlds. Once his memories return, he grants Tsukikage permission to initiate the Rider Battle, confirming his role as the leader.

Tsukasa's photos of his home world and his familiarity with the mansion hint that this world is deeply connected to his past.

Sayo Kadoya is Tsukasa's younger sister who reveals herself when the team arrives at the mansion in the AR World. She immediately recognizes Tsukasa as her older brother, though he has lost most of his memories of her. Tsukikage confronts Tsukasa about abandoning his sister for a year, creating tension between past loyalties and present dangers.

The mansion in the backdrop and Tsukasa's recognition of it hint at his personal connection to this world.

The Rider Battle is a contest Tsukikage proposes to resolve the crisis of the Nine Worlds fusing with the World of Decade. The concept suggests that the strongest Kamen Rider's victory would decide the fate of all realities. Tsukasa's memories return as he grants Tsukikage authority to set this plan in motion, leading to a multiverse showdown.

Tsukikage explains that Tsukasa's journey has unlocked this possible solution to the world-fusion crisis.

Nobuhiko Tsukikage is revealed to be a double agent working for Dai-Shocker all along. While presenting himself as a caretaker for Sayo, he is actually Shadow Moon, one of Dai-Shocker's most powerful warriors. His scheme involves using the Rider Battle and the Stone of the Earth to unleash Kuuga's ultimate power and advance Dai-Shocker's plan for global domination.

Tsukikage's stern confrontation about Tsukasa abandoning his sister foreshadows his deeper manipulation.

The Stone of the Earth is a powerful artifact used by Sayo to amplify Dai-Shocker's schemes. When she uses it on Yusuke Onodera, it pulls Kuuga's greatest form, the Rising Ultimate Kuuga, into him, creating a powerful but controlled weapon that threatens both Natsumi and Yusuke's safety. Sayo later pushes away the Stone's control, freeing Yusuke from its grasp.

The Stone is introduced as the key to pulling Kuuga's greatest form into the picture.

Yusuke Onodera receives Kuuga's ultimate power when Sayo uses the Stone of the Earth on him. This activates Rising Ultimate Kuuga, the most dangerous and powerful form of the Rider, within Yusuke. The transformation is controlled by Dai-Shocker initially, but Sayo later breaks the control, freeing Yusuke to fight alongside the other Riders.

Tsukikage reveals that the combined power of the Stone could pull Kuuga's greatest form into the picture.

Jōji Yūki confronts Tsukasa seeking revenge for his lost arm and his faction's downfall. However, he realizes Tsukasa has changed and is now a target for Dai-Shocker. In a pivotal moment, Yūki sacrifices his robotic arm to help Tsukasa escape and transform into Riderman, showing his shift from enemy to ally.

Yūki's initial revenge motive sets up his unexpected turn toward mercy and change.

Kamen Rider W, the dynamic duo of Shotaro Hidari and Philip, makes a timely entrance during the final battle. Their appearance helps turn the tide against Dai-Shocker's forces. W takes on Shadow Moon with a swift, decisive strike and defeats him, pinning him in the castle and clearing the way for the All Rider Kick.

The arrival of the Riders to assist Decade sets up the coordinated assault on Dai-Shocker.

King Dark is a primal force awakened by the destruction of Dai-Shocker's castle. When the All Rider Kick shatters the castle and defeats the main villain forces, the blast awakens King Dark, who rises in the aftermath as the most perilous breach between the universes. He becomes the final threat that requires the combined power of Decade and Kamen Rider J to defeat.

The text explicitly states the blast awakens King Dark in the wake of the castle's destruction.

After King Dark's emergence, Diend arrives with Kamen Rider J and uses the DecaDriver Final FormRide card. This transforms Decade into Jumbo DecaDriver while simultaneously evolving J into Decade Complete Form Jumbo Formation. This combined form delivers the Dimension Kick that defeats King Dark and closes the dangerous breach between universes.

Diend's arrival with J and the use of a Final FormRide card set up the ultimate finishing move.

After the battle concludes and Tsukasa makes amends with Sayo, Tsukasa returns to the Hikari Studio, his true home. Eijiro Hikari (Doctor Shinigami) reappears as if nothing happened, signaling that the bond between worlds is both broken and rebuilt. This leaves the door open for future twists and suggests the multiverse's reality is malleable based on faith and memory.

The film establishes that Dai-Shocker operates across saved worlds, making reality fluid.