オーバーロード - 時は2138年。仮想現実の中を自由に遊ぶことのできる体感型ゲーム全盛の時代に一大ブームを巻き起こしたオンラインゲーム《ユグドラシル》は静かにサービス終了を迎えるはずだった。
しかし、終了時間を過ぎてもログアウトしないゲーム。
突如として意思を持ち始めたNPCたち。
ギルドの外には見たこともない異世界が広がっていた。
現実世界ではゲーム好きの孤独で冴えない青年が、骸骨の姿をした最強の大魔法使い・モモンガとなり、彼の率いるギルド《アインズ・ウール・ゴウン》の伝説が幕を開ける!
Overlord - The final hour of the popular virtual reality game Yggdrasil has come. However, Momonga, a powerful wizard and master of the dark guild Ainz Ooal Gown, decides to spend his last few moments in the game as the servers begin to shut down. To his surprise, despite the clock having struck midnight, Momonga is still fully conscious as his character and, moreover, the non-player characters appear to have developed personalities of their own!
Confronted with this abnormal situation, Momonga commands his loyal servants to help him investigate and take control of this new world, with the hopes of figuring out what has caused this development and if there may be others in the same predicament.