The Scholar Who Walks the Night

What is The Scholar Who Walks the Night about (plot, summary)
In Joseon Dynasty, immaculately dressed in scholarly robes, the young nobleman Kim Sung Ryul lives as a vampire to keep his promise to his friends. When Sung Ryul still was a human, he found out about the vampire Gwi who sits above the King deciding the next royal line and has resurrected as a vampire trying to fight against Gwi. And now, he is living as a guardian vampire fighting against the evil vampire without losing his human nature.