Masked Rider Decade

The story revolves around the nine previous universes of the Kamen Riders from the Heisei era 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 (referred to as an A.R. World or Another Rider's World) and eliminate the anomaly in that world.