Demon World

Demon World (魔界), sometimes refers to Devil's World, is a term used in describing the home world of monsters.

Kamen Rider Black RX
In sort of situations, the term Demon World was equals to Strange Demon World.

Kamen Rider Kiva
The term was used in various titles related to this series:
 * Kamen Rider Kiva: King of the Castle in the Demon World (Movie)
 * Kamen Rider Backwards-Kiva: Queen of the Castle in the Demon World (Net Movies)
 * DokiDoki Makai Castle Kiva (Game)

Movie War Ultimatum
In Kamen Rider × Kamen Rider Wizard & Fourze: Movie War Ultimatum, Demon World is the home of the Akumaizer trio and their race, Akuma Clan.