Ainz Ooal Gown, the sorcerer who transformed into an undead being known as Momonga, has accepted his new existence in a world reminiscent of his virtual game, Yggdrasil. This dimension is full of mysteries, and Ainz is determined to uncover them all using his dominion over the Great Tomb of Nazarick. However, after one of his supporters was brainwashed, he worries about potential harm from the Slane Theocracy and other ex-Yggdrasil players. Meanwhile, Albedo, Demiurge, and the other loyal guardians are preparing for Nazarick's inaugural battle. Overlord II continues the previous installment's storyline, exploring Ainz and his group's animosity towards humans, as well as the unfortunate individuals who are affected by their arrival.