The story revolves around the nine previous universes of the Heisei Kamen Riders merging into one, something that would destroy all the worlds. To prevent this, Tsukasa Kadoya transforms into Kamen Rider Decade and is told that to protect his own world he must travel with Natsumi and her grandfather to the other Kamen Riders' Worlds called A.R. Worlds (Another Rider's World or Alternate Reality World) and eliminate the anomaly in that world. Along the way, confronting the mysterious Narutaki and the thief Daiki Kaito, they are joined by Yusuke Onodera of the World of Kuuga and Kivala of the World of Kiva.To fit with the photography motif of the series, the main Kamen Riders of the series follow the CMYK color model: Decade is magenta, Diend is cyan, and Kuuga (Ultimate Form) is black. While no specific Rider has been yellow, the armor of Kuuga Rising Ultimate is yellow (gold). In the Cho-Den-O Trilogy film Episode Yellow: Treasure de End Pirates, Diend is the primary character, emphasizing the yellow accents on his Diendriver & card.