The Demon Realm

Setting
Demon World is the world where demons live, that looks strangely like Feudal Japan. It is an alternate dimension that King Enma sealed off with a powerful barrier which forbade any demon ranked A Class or higher to cross. For many years it was ruled by 3 kings: Toshin Raizen, Mukuro and Yomi, though not in the literal sense. There was no set government, only territories over which the 3 demons ruled; these territories were formed out of the natural chaotic state of the environment. Despite the order that they brought in accordance to the times and intricacies, they could be attacked at any time and no rules would be broken because there weren't any to begin with. In other words: the rule over a territory all came down to who had the greatest strength and ambition, much akin to the real-life criminal underworld.

The Demon Kings
1. Toshin Raizen - Tourin Territory
2. Mukuro - Alaric Territory
3. Yomi - Gandara Territory

Geography
Each territory had its own individual laws, as established by its rulers, until the establishment of the Demon World Tournament, whose victor would unify Demon World under him/her as the supreme ruler. Raizen, Mukuro, and Yomi are acknowledged as the three kings because out of all the kingdoms in the land, they have the greatest influence and strength to negotiate a deal with King Enma to allow Yusuke, Kurama, and Hiei to return to Demon World.

Demon City, which is occupied by the Four Saint Beasts, and Hyouga the Island of the Koorime are distinct territories that did not appear to be under direct control of any of the 3 demon kings. Demon World is rather like an endless basement, with its strongest demons living deeper and deeper within its depths. With its surface inhabited by demons of fair power and notoriety, demons within its ultimate depths are said to be god like and mere embodiment of destruction.

Technology
Much of this world seems to be terrains, including untouched wastelands, forests, mountainous regions, deserts etc. However, despite this natural and primitive environment, Demon World's technology surpasses that of Earth Realm (Modern Day), as healing chambers and artificial birth machines have been employed by the three kings on different occasions. Also, Demon World seems to have cities with technologies such as television as seen during the Demon World Tournament.