|Name: Tsukasa Kadoya|
|Designation: Kamen Rider Decade|
|Weapons: Ride Booker|
|Gear: Decadriver, Rider Cards, K-Touch|
|Tsukasa Kadoya is a young photographer who doesn't know much about his past. He has a strong desire to 'catch the world' taking pictures with his Blackbird, fly 135 Twin Lens Reflex Camera, but they develop strange looking. As Decade, he is seen as an abomination, a rumor spread by Narutaki, who believes Tsukasa doesn't belong in any world. It is also revealed that those who appear in his badly developed photographs have some fate befall them, be it death or otherwise. As Tsukasa travels between dimensions, specific clothing appear on him reflecting said dimension and sometimes exhibits some prior knowledge or a talent for the world. Examples to this are his Grongi language knowledge in the Kuuga World and his enrollment as a student in the Faiz World.
It is revealed that Tsukasa was the Great Leader of Dai-Shocker, an evil organization that is attempting to take over all dimensions. He commissioned the creation of the Decadriver in order to prevent the collapse of the A.R. Worlds and allow Dai-Shocker to conquer them. Tsukasa somehow suffers from amnesia and ends up in Natsumi Hikari's home dimension, where he gets the Decadriver and becomes Kamen Rider Decade. Finally, after fighting Dai-Shocker through the alternate worlds, he and Diend kill the last of the Dai-Shocker's active Leaders, Super Apollo Geist. However, it is eventually revealed that his true mission was to destroy the A.R. World Riders and their worlds, a role he undertakes as the Rider War commences, becoming Kamen Rider Decade Fury Form.
While he destroys all the other Kamen Riders except for Diend, Natsumi uses Kivara, to transform into Kamen Rider Kivara. Decade then willingly allows Kivara to impale him through the Decadriver. As she does this, he gives her the cards left behind when he killed the other Riders. His death is the catalyst for the restoration of all the A.R. Worlds and everyone who died in the Rider War, even those Decade didn't kill personally. Afterwards, the memories of his friends are used to revive him and he leads the other Kamen Riders in the final battle with the newly formed Super Shocker and the revived Neo Organism. After a long, fierce battle, he teams up with Kamen Rider Double to destroy the Super Crisis Fortress and use the Triple Extreme Kick to destroy the Neo Organism in the form of Ultimate D. Afterwards, he and his friends return to the Hikari Studio to continue in their journey across the A.R. Worlds.