The story begins when Yggdrasil, a popular online game is quietly shut down one day. However, the protagonist Momonga decides to not log out until the end. Momonga is then transformed into the image of a skeleton as "the most powerful wizard." The world continues to change, with non-player characters (NPCs) beginning to have personalities. Having no parents, friends, or place in society, this ordinary young man Momonga then strives to take over the new world the game has become.