|This article is about a/an alternate reality/A.R. World (another rider's world) in Kamen Rider Decade.|
The World of Kuuga (クウガの世界 Kūga no Sekai?) is the alternate reality where a version of Kamen Rider Kuuga takes place. It was the world where Yuusuke Onodera originated from before he joined Tsukasa in his journey. The backdrop used to arrive in this world shows a city with police cars and Mount Hitoki (灯溶山 Hitoki-yama?) in the background. Within this A.R. World, Tsukasa assumes the guise of a police officer with the talent of understanding and speaking the Gurongi language.
- Yuusuke Onodera - this world's native (and only) Kamen Rider
- Ai Yashiro - died in episode 3
- N-Gamio-Zeda - the ultimate darkness
- Gurongi - Gamio's attendants, they tried to revive him through the ultimate game
In the novel reimagination of the Kamen Rider Decade TV series, Kamen Rider Decade: The World of Tsukasa Kadoya ~The Garden Inside the Lens~, the World of Kuuga is, as one of the Nine Worlds, not an alternate reality like in the TV series but the original world. Having already traveled to six worlds, the World of Kuuga is the second of the three remaining worlds the Hikari Studio group, Tsukasa/Decade, Kaito/Diend, and Natsumi, explore during the novel.
Kuuga’s world is set somewhere early in the TV show, where Kaoru Ichijo is the only person who considers Kuuga to be an ally of humanity, while the rest of the police forces consider Kuuga as a threat. Despite having the name Yusuke Godai, his personality is actually closer to Onodera’s, if anything. Godai is an airhead for the most part, to the point of having difficulty remembering the name Decade and usually goes with “Kamen Rider Dickens.” In this world, Tsukasa is dressed as a painter in Kuuga’s world. Despite being Kuuga’s world, Tsukasa doesn’t interact much with Godai.
Instead he meets a mysterious unnamed girl, with her sentences spoken in broken grammar. This girl approaches different men saying “Do you want me?” The girl is referred as Yuri after Tsukasa sees her holding a lily flower, yuri in Japanese. She asks the question to Tsukasa, but Natsumi doesn’t like it and uses her Laughing Pressure Point technique. Yuri takes a liking to Tsukasa and connects with him. Tsukasa says they are the same type of people, and relate to each other. But he reveals that he never really paid attention to her and never cared about her. From the start, Natsumi oddly suspects that Yuri is a Gurongi. This is never truly touched upon until the where Yuri reveals the truth and challenge the Riders into a fight. Her Gurongi group is not mentioned, but she’s described as a Moth, meaning she's of the Ba class of Gurongi. She causes people to explode by sticking moth scales from her wings on people. Decade and Kuuga defeat her together. Godai only uses Mighty and Dragon, but for some reason he’s using a sword while in Mighty form, which has traditionally been a form more focused on hand-to-hand combat. Decade's Final Form Ride for this Kuuga is also different: while it retains the ability to transform Kuuga into the Kuuga Gouram, the Gouram is described as a rhinoceros beetle, despite it traditionally being a stag beetle, which is also the same insect Kuuga is based on. Godai gives Tsukasa a thumbs up as they leave.