The Vampire of the East (2012)

Blurb:
After the decline of her family, Yangsun finds herself living as a book seller, while hiding her real identity. One day, she visits Eumseokgol to deliver some books. She runs into a breathtakingly beautiful scholar, Sungyul Kim, who is actually a vampire in disguise! As much as they are drawn to each other, they can’t be together because of the fact that one of them is human and the other, is a vampire! Could their love come to fruition? The mystery of the palace from the Chosun dynasty adds to the excitement.

Source: www.anisearch.com/manga/17893