Yggdrasil is a virtual reality game renowned for the freedom it offers its players. After a simple tutorial, players are left to explore the world and can customize anything and everything, from their classes to their weapons. However, in the year 2138, the game sees its final hours as its servers shut down at midnight.

Momonga, a devoted player of Yggdrasil, decides to spend the game's last hours inside his guild, Ainz Ooal Gown. Strangely, at the stroke of midnight, the game does not log him out. Instead, Momonga finds himself transported to another world, one that is seemingly identical to that of Yggdrasil. Facing an already abnormal situation, he discovers that the NPCs have gained sentience.

Trapped in his avatar's skeletal body and desperate to uncover the cause of his predicament and find other players like him, Momonga sets out to take control of the new world with the help of his loyal subjects.