Sousouki Reginald

A thick mist covers the city of Faith-Delhi constantly. In the mist and smoke of this metropolis, demons known as "Pagans" lurk in the shadows. Pagans are born when humans fail to join the other souls in the path to reincarnation. There is a group known as the "Twanbach Funeral Service Company" who specializes in hunting these Pagans. Reginald, a 100+ year old vampire that looks like he's 20 years old, gets hired by the Twanbach company by the mysterious twins, Vanessa and Veronica Twanbach.

(Source: MangaHelpers)