"Overlord" is a dark fantasy manga series adapted from the light novels written by Kugane Maruyama and illustrated by so-bin. The narrative centers on Momonga, a powerful wizard and the leader of the guild Ainz Ooal Gown in the virtual reality MMORPG Yggdrasil. As the game's servers are set to shut down, Momonga decides to stay logged in until the very end. However, when the shutdown time passes, he finds himself still in the game world, which has transformed into a fully realized reality. His character, now known as Ainz Ooal Gown, retains all his abilities and powers, and the NPCs of his guild have gained sentience, treating him as their supreme ruler.

The story explores Ainz's efforts to understand this new world and uncover the reasons behind his transformation. He adopts the persona of an undead overlord to maintain authority over his loyal NPC subordinates, who revere him as their creator. Among these NPCs are Albedo, the Overseer of the Guardians, who harbors an obsessive love for Ainz; Demiurge, a cunning strategist; and Shalltear Bloodfallen, a powerful vampire. Together, they form the backbone of Ainz's rule over the Great Tomb of Nazarick, the guild's former headquarters, now a sprawling dungeon filled with traps, treasures, and formidable guardians.

As Ainz ventures into the world beyond Nazarick, he encounters various factions, kingdoms, and races, each with their own agendas and power structures. His interactions range from diplomacy to outright conquest, as he seeks to expand his influence and gather information about the world's mysteries. The series delves into themes of power, morality, and identity, as Ainz grapples with his undead nature and the ethical implications of his actions. Despite his immense power, he often relies on caution and strategy, fearing the existence of other players or entities that could rival his strength.

The plot is driven by Ainz's dual goals: to uncover the truth behind the world's transformation and to ensure the survival and prosperity of Nazarick. Along the way, he faces numerous challenges, including internal conflicts among his subordinates, external threats from rival factions, and the moral dilemmas of wielding absolute power. The series balances large-scale battles, intricate political maneuvering, and character-driven moments, offering a multifaceted exploration of its dark and complex world.