Saikyou Vampire Ou no Chikara de Musou Suru

The vampires have conquered the entire world. Hibiki belongs to "The Resistance," a group opposing the vampires' rule, but he's weak and treated as a nuisance, all the while having nightmares of vampires doing as they please with humans. However, when he is unable to protect Captain Maria, whom he respects very much, Hibiki is killed. He then meets the soul of Vlad, the vampire king who was killed by his kin in a rebellion 500 years ago, and obtains his power! It may be the power of the Vampires he loathes, but Hibiki is willing to accept it to protect the people he cares for!