In the year 2039, the drastic effects of global warming have caused sea levels to rise, resulting in major loss of land. To ensure humanity learns its lesson, a fleet of powerful warships equipped with advanced weaponry emerges, causing overwhelming defeat for naval forces throughout the world. Calling themselves the Fleet of Fog, each ship has a "Mental Model," a humanoid avatar which represents the ship's heart, its "Union Core." Each model has a different personality but all follow an unknown authority known as the Admiralty Code, who have implemented a blockade to prevent humans from traveling across the sea. Seventeen years after the blockade, Gunzou Chihaya, a National Marine Academy alumnus, stumbles upon I-401 and its Mental Model, Iona, who sides with mankind for unknown reasons. Utilizing this newfound hope of achieving peace for humanity, Gunzou and his friends form a group of privateers, known as the Blue Steel, as they set out on a dangerous journey.

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.

Vash the Stampede is a contradiction. He has a notorious reputation as "The Humanoid Typhoon," laying anything he comes across to waste on the desolate planet of Gunsmoke. However, Vash is in fact very non-confrontational and kind-hearted, living by a code of pacifism. Twenty years ago, a high-profile bank heist went sour. The ringleader, Gasback Gallon Getaway, swore to get back at his backstabbing crew and the man who stopped him from killing them: Vash the Stampede. In the present day, the traitorous crew has been living the good life as successful entrepreneurs and politicians. Although two decades have passed, Gasback's bitterness has not waned as he aims to take them down one by one, by any means necessary. Just in time to foil Gasback's plot, Vash has arrived in Macca City. Teaming up with the mysterious Amelia Ann McFly, along with the insurance agents Milly Thompson and Meryl Stryfe, Vash is ready to rumble.