|This article is about a/an rider who never transformed (rider exists only as a toy) in Kamen Rider Decade.|
|Joji Yuki (A.R. World)|
|Series:||Kamen Rider Decade|
|Motif:||Mantis, V3-Mantis Suit|
|Homeworld:||Earth (World of Decade)|
|First Appearance:||Kamen Rider Decade: All Riders vs. Dai-Shocker|
|Last Appearance:||Kamen Rider Decade: All Riders vs. Dai-Shocker|
|Number of Episode|
- "Sins do not disappear. All you can do is live on bearing them. Even if alone, you fight as long as you live. That is a Kamen Rider, isn't it?"
- ―Joji Yuki[src]
He is a mysterious young man with a prosthetic arm who has the ability to become Riderman. He was a scientist who worked for Dai-Shocker and was involved in the production of the Decadriver and the Diendriver. For unknown reasons, Yuki was punished, had his arm amputated, but survived and rebelled against Dai-Shocker. This made him a wanted man in the Decade World. He hated Tsukasa for cutting his arm, but, by the time he finally was face to face with him, he was a changed man, and Yuki decided not to kill him but help him escape from Dai Shocker.
In the manga adaptation of All Riders vs. Dai-Shocker, Yuki appears and turns into Riderman. His face is obscured but the implication is it's the Gackt version. However, the form he takes is that of classic Riderman. The other Riders show up with him.
- Blaster/Cannon Arm (ブラスター/キャノンアーム Burastā/Kyanon Āmu?): This weapon is used while he is in human form. It is activated when Joji rips off his prosthetic arm and attaches the weapon part onto himself. This is seen in Kamen Rider Decade: All Riders vs. Dai-Shocker and in "The Next Decade" MV.
- Reportedly, Toei wanted to design a modernized Riderman costume, but it couldn't be completed in time and so Gackt only appears as Joji Yuki and never transforms.
- Gackt is only credited in the film as Joji Yuki, not Riderman.
- In the Music Video of "The Next Decade", his name is spelled as "Joji Yu-Ki" in the wanted poster with a bounty of $100,000.
- In interviews, Gackt has said that when offered a role in the movie, he chose Riderman because Yuki fights evil despite being just an ordinary man, unlike the other Showa Riders who possess cybernetic enhancements.