|Natsumi Hikari had a dream of various Kamen Riders fighting in the Rider War and the victor was a mysterious Kamen Rider Decade. When evil forces attack her world, her grandfather's employee Tsukasa Kadoya receives the Decadriver and becomes Kamen Rider Decade. All dimensions are colliding and Natsumi's dimension is being frozen. Tsukasa is told that in order to protect his dimension, he must travel to the Another Rider's Worlds and eliminate the anomaly. He travels with Natsumi and her grandfather within the Hikari Photo Studio, with backdrops changing and they each reflect one aspect of the world. There is nine A.R. Worlds, based on the past nine Heisei series. Yusuke Onodera of the Kuuga World, he is unwittingly sent by Kivara and joins with the Hikari Studio group, after getting rid of the Grongi from his dimension. Tsukasa actually befriends the main Kamen Riders of the Worlds instead of destroying them, the mysterious Narutaki kept telling the other world inhabitants that Tsukasa would destroy them.
In the Blade World, Daiki Kaito reveals himself to Tsukasa, being an ally sometimes and others not, he seems to know more about Tsukasa than he even knows. Daiki transforms into Kamen Rider Diend and steals various things from different worlds, calling them treasures. After visiting the Hibiki World, the Hikari Studio group end up where Natsumi believes it is home. She goes to high school and reunites to her friends and find out that unfortunately that it is the Negatives World and everyone is evil. There she meets the Natsumi of that world. After that world, they go to the World of Diend, where they find out Daiki was the most wanted and his brother is Kamen Rider Glaive and their world is under-siege by the Fourteen. After the Fourteen are defeat, Daiki proceeds to steal the Ika Origami from Genta Unemori in the Shinkenger World. The others eventually find themselves there, Tsukasa in the clothes of the Kuroko, he infiltrates the Shiba House. Natsumi doesn't take it well when she hears that it is a world without Kamen Riders.
An Ayakashi steals the Diendriver and becomes a Kamen Rider hybrid, threatening all reality. The Shinkenger and Kamen Riders team up and destroy the threat, Genta and Daiki exchange the Ika Origami for the Diendriver. After that visit, they continue to the World of Black and the World of Black RX, World of Amazon, and finally the World of the Rider War. Dai-Shocker make their presence known and plan to take over all dimensions. Ultimately, Tsukasa is the key to all the worlds' survival.