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.

Ainz Ooal Gown, the undead sorcerer formerly known as Momonga, has accepted his place in this new world. Though it bears similarities to his beloved virtual reality game Yggdrasil, it still holds many mysteries which he intends to uncover, by utilizing his power as ruler of the Great Tomb of Nazarick. However, ever since the disastrous brainwashing of one of his subordinates, Ainz has become wary of the impending dangers of the Slane Theocracy, as well as the possible existence of other former Yggdrasil players. Meanwhile, Albedo, Demiurge and the rest of Ainz's loyal guardians set out to prepare for the next step in their campaign: Nazarick's first war… Overlord II picks up immediately after its prequel, continuing the story of Ainz Ooal Gown, his eclectic army of human-hating guardians, and the many hapless humans affected by the Overlord's arrival.

Young Ciel Phantomhive is known as the Queen's Guard Dog, taking care of the many unsettling events that occur in Victorian England for Her Majesty. Aided by Sebastian Michaelis, his loyal butler with seemingly inhuman abilities, Ciel uses whatever means necessary to get the job done. But is there more to this black-clad butler than meets the eye? In Ciel's past lies a secret tragedy that enveloped him in perennial darkness—during one of his bleakest moments, he formed a contract with Sebastian, a demon, bargaining his soul in exchange for vengeance upon those who wronged him. Today, not only is Sebastian one hell of a butler, but he is also the perfect servant to carry out his master's orders—all the while anticipating the delicious meal he will eventually make of Ciel's soul. As the two work to unravel the mystery behind Ciel's chain of misfortunes, a bond forms between them that neither heaven nor hell can tear apart.

There exist creatures of darkness and evil that plague the night, devouring any human unfortunate enough to be caught in their grasp. On the other side is Hellsing, an organization dedicated to destroying these supernatural forces that threaten the very existence of humanity. At its head is Integra Fairbrook Wingates Hellsing, who commands a powerful military and spends her life fighting the undead. Integra's vast army, however, pales in comparison with her ultimate weapon: the vampire Alucard, who works against his own kind as an exterminator for Hellsing. With his new vampire servant, Seras Victoria, at his side, Alucard must battle not only monsters, but all those who stand to oppose Hellsing, be they in the guise of good or evil. In a battle for mankind's survival, Hellsing Ultimate proves that appearances are not all they may seem, and sometimes the greatest weapon can come in the form of one's worst nightmare.