This article is about a/an set of alternate worlds in Kamen Rider Decade.

The characters of Kamen Rider Decade exist amongst various iterations of reality within the series referred to as an A.R. World (Another Rider's / Alternate Reality World). The Nine Worlds (9つの世界 Kokonotsu no Sekai) are the A.R. Worlds that are based on the previous entries of the Kamen Rider Series that have aired during the Heisei period of Japanese history. Each differs in some way from the series on which it was based. The New Worlds (新たな世界 Aratana Sekai) are the A.R. Worlds that are not based on a previous entry of the Kamen Rider Series from the Heisei period.

A.R. Worlds

Originally, Tsukasa only knew that their destinations were nine A.R. Worlds to finish their journey. As the story progressed, they realized that their journey doesn't end at the ninth world, but further more towards new worlds, until Decade connects these worlds' stories through him. The A.R. worlds are alternate realities in Decade's point of view.

Nine Worlds

New Worlds


Unidentified A.R. Worlds

"Another Hell"

Delta and Tiger (Decade)

Delta and Tiger awaiting the Hell Brothers.

This A.R. World contained iterations of Kamen Riders Tiger and Delta, whom appeared as shadows in a dimensional wall brought forth by Narutaki to take the Hell Brothers KickHopper and PunchHopper out of the World of Kuuga. Judging from KickHopper's comment "Another hell awaits.", it can be assumed that the two Riders were waiting to fight them. Transcendence

"World of Kaixa"



This A.R. World was home to an iteration of Kamen Rider Kaixa, Masato Kusaka. By influencing the dimensional walls, Kiva-la brought Tsukasa from the World of Kiva to this world where he was attacked by Kaixa, who was under the impression that Decade was a hindrance to his own agenda, seeking to take the Decadriver from him. Second Movement ♬ Prince Kiva He eventually conceded when Decade was returned to the World of Kiva. The Biting King's Qualifications

"World of Ryuga"



This A.R. World was home to an iteration of Kamen Rider Ryuga, Dark Shinji. Tsukasa was briefly brought to this world from the World of Faiz by a dimensionall wall manifested by Narutaki who, having had Kaito deprive Tsukasa of his Ride Booker, intended for Ryuga to kill the defenseless Decade. However, after interrogating Kiva-la on his whereabouts, Daiki intervened while claiming it was to get the Faiz Gear as he returned the Ride Booker to Tsukasa.

Proceeding to engage Ryuga, Diend summoned Kamen Rider Kiva ("A monster for a monster.") when Ryuga summoned Dragblacker, transforming him into his Final Form Ride Kiva Arrow form soon after. He used Kiva Arrow's Final Attack Ride to counter Ryuga's Final Vent. Diend's final attack prevailed, seemingly destroying both Ryuga and Dragblacker. 555 Faces, 1 Treasure

"World of Skull"

AR Soukichi Narumi

Another Sokichi Narumi, introducing himself to Shotaro Hidari.

This A.R. World is home to an alternative version of Sokichi Narumi, who transformed into Kamen Rider Skull like his prime counterpart. He was, however, unfamiliar with Shotaro Hidari. By leaving him with the Rider Card, Kamen Ride: Skull, Tsukasa enabled the prime Shotaro, whose Sokichi Narumi had been killed during Begins Night, to meet the alternate Skull who briefly visited his world through the dimensional wall. Kamen Rider × Kamen Rider W & Decade: Movie War 2010

Worlds with no relation to Decade


In the novel re-imagination of the Kamen Rider Decade TV series, Kamen Rider Decade: The World of Tsukasa Kadoya ~The Garden Inside the Lens~, the Nine Worlds are not alternate realities, but in fact the original worlds. The Hikari Studio group has already traveled to 6 different worlds when the novel begins, leaving only Den-O, Kuuga and Kabuto’s world unexplored.