Dungeon Battle Royale

One day, a mysterious email goes out to everyone across Japan containing one simple command — take this aptitude test, or be branded "Neutral." College loner Shion initially ignores the message, but when news of the strange aptitude test floods the media, he decides to try it out...and receives the designation "Chaos." Soon after, the world is transformed by a mysterious young girl into a video game-style RPG battle royale between the classic Dungeons and Dragons alignments of Law and Chaos. The goal: motivate humanity from the brink of extinction by exposing them to some real conflict. As a newly-minted demon lord, Shion has to learn to play the game...or face conquest by adventurers eager to loot his stronghold and level up.

(Source: Mangamo)