It's the story of a vampire, whose parents were killed during his childhood. he therefore has come to hate humans, that is until he met a boy who later on becomes a priest I think. the vampire collaborates with this boy to save humans, and he falls in love with an aristocratic girl who doesn't know what he is. It's set in a medieval-like era, and is a manhwa or manua rather than a manga i think. If you can help me find the title, that would be great!

Sounds like Rebirth been awhile since i read it so im not 100% sure it sounds alot alike in the flashback part.