Kyo Kara Maoh!, takes place in an alternate world that Yuri Shibuya travels to by coming in contact with water. It is the first time he is transported to the other world when he tried to save his former classmate from bullies and ended up getting attacked by them instead. They took him into a girls restroom and shoved his head in a toilet. The next thing he knows, he's in a world that vaguely resembles medieval Europe. Yuri is told he was called there because he is the new Demon King (魔王 Maoh?, Mazoku King)
There are many nations in the alternate world, however, the plot centers around the The Great Demon Kingdom (眞魔国 Shin Makoku?, True Mazoku Land). The people of the kingdom are Demons (魔族 Mazoku?), but appear indistinguishable from humans. Their only distinguishing traits are their long lives and the ability to use magic. The people of the Demon Tribe are able to make a pact with an element which they can then use magic of that element. Covenant Castle is in the capital of the Demon Kingdom. It is the residence of the demon king. The culture of The Great Demon Kingdom is very different from the Japanese culture Yuri is accustomed to, and the differences make for some amusing mishaps with long ranging consequences, such as an accidental proposal of marriage.