I'M NOT BIG ON ANIME (anymore) BUT THIS REALLY MAKES ME HAPPY AND I HOPE THEY ADAPT IT INTO A FULL SERIES
The basic plot of this OVA is the first arc of the Vassalord manga (sort of).
Vassalord is about a vampire hunting cyborg priest who also happens to be a vampire (Charles Crishunds/Chris Michel/Charlie/Cherry) and his vampire master, a playboy rich guy (Johnny Rayflo) who is also a 2000+ year old true vampire, so old that his vampire name was "Adam" with biblical connotations. The two have a complex relationship and slow-burning love, while having to deal with this new drug called Vassalord that's turning humans into vampires--or killing them.
Other characters include Craig, an older black detective from America; Rayfelle, the Eve to Rayflo's Adam (who looks exactly like Rayflo but female), Cheryl, the young female vampire huntress who calls Rayfelle master, 86, a mad assassin who is a cross between Deadpool and a puppy, and others.
*****Read it here. ******
If I had to describe this manga, I'd call it the gay lovechild of Blade and Hellsing with Phantom of the Opera and biblical references.