|This article is about a/an character in Kamen Rider Decade.|
- "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. He was a scientist who worked for Dai-Shocker and was involved in the production of the Decadriver and Ride Booker, as well as the Diendriver. However, Yuki was branded a traitor and hence was punished, had his arm amputated, but survived and rebelled against Dai-Shocker. This made him a wanted man in the world of Decade. He hated the Great Leader, Tsukasa Kadoya, 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 it is implied to be this A.R. World version. However, the form he takes is that of classic Riderman. The other Riders show up with him.
- See also: Cassette Arms
- 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.
- 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 Yuki because Yuki fights evil despite being just an ordinary man, unlike the other Showa Riders who possess cybernetic enhancements.
- This A.R. World Riderman marks the first Heisei Era Rider who is played by the singer who sang the opening theme, coincidentally at 5 years later, a Kamen Rider who "stole" Riderman's "Kamen Rider 4" title would be voiced by a singer who also sang a opening theme.