Demon World

The Demon World, or Hell, is Neuro's home universe, where other demons like him reside as well. The reason why Neuro left the Demon World was because he had already eaten all of its mysteries, as well as saying that they only had "one kind of flavor": simple, bland and repetitive; and that only in the Human World his need for the ultimate puzzle could be satisfied.

Throughout the series Neuro tells about his life in the Demon World, but this usually comes off as nonsensical, so it is unknown if this is true information. Moreover, through Neuro's explanations, the Demon World is always portrayed like a chaotic, deserted place, similar to the concept that humans have about hell; as well as portraying the residents as grotesque creatures.

A known (and confirmed) fact about this world is that the dimensional and time axes differ greatly between the Demon World and the Human World. For instance, if Neuro were to return to Hell, and then come back to the Human World, it could be a year, or a thousand years later, or he could even end up at a parallel universe of the world above. From this, as well as some other random facts Neuro has stated (see below), it can be inferred that even though Hell is "below" the human surface, it belongs to a completely different universe.

Although not much is known about Hell's ecosystem, creatures, and such, there are many random facts that Neuro has given about the Demon World that give a general idea of what that universe is like.

Facts about the Demon World

• There are few kinds of food in the Demon World: some cause you to catch fire; or you could eat things in several places and everyone would be watching.
• In Hell, a person like Yako Katsuragi is usually stuck in one place for eternity.
• There seems to be different types of demons, as Neuro states that he has similar acquaintances that are able to control the brain (unlike him).
• Soap operas in the Demon World are very simple; usually during the first five minutes everyone dies, and after that the dead bodies are filmed the whole way through.
• Although the dimensional and time axes are different in Hell, they seem to use the same time standard as humans.
• A good person in the Demon World is someone who joyfully scoops out open wounds, and likes to make recovery impossible.
• There are those who have superb hair in the Demon World: its total length is 420km (around 261 miles); it attacks under cover of darkness; and for the purpose of "hairstyling" it sucks the life from the living things around it at random. This hair is envied throughout Hell.
• Desks in the Demon World are different from the ones in the Human World: if something is placed on them, they snap and go out of control, and then make the person do the work.
• A kidnapping in the Demon World has its own varieties of hostages, like kidnapping a continent for several thousand years.
• There are video games in the Demon World; but their genres and meaning of fun are entirely different: Neuro's Evil Station can play a game similar to Sim Dating, but to blurt out their love the players have to be brutally killed.