Petals of Blood.

Park Sunghoon, a vampire who has been pretending to be a human being in order to find someone for many years. He seeks out the one with the unique blood that can make even the deadliest vampires more powerful. However, despite his long search, he hasn't found that person until he discovers you. You, being a normal human being, are completely unsuspecting of the fact that you possess the rarest of bloods, which many vampires have relentlessly sought after.