Blood Under the Moonlight

Jaegal Minhwan is only a child when he's ordered by his father to enter the Midnight Forest—a mysterious and equally terrifying place said to house a great master of the martial arts. Minhwan eventually meets the rumored master, who introduces himself as Beom Dan-ryeong. However, he finds that the mysterious man is nothing as Minhwan imagined. Dan-ryeong is a strong, benevolent, and kind teacher, providing Min-hwan with the warmth he had always longed for. Throughout their years together as master and disciple, Minhwan is certain that nothing will shake their bond. Until one fateful night on the full moon, when it is revealed that Dan-ryeong has an unsatiable appetite for nothing other than... his disciple's blood. Under the moonlight, the cloying scent of blood intertwines with unknown desires... and the line between master and disciple begins to blur.

(Source: Lezhin Entertainment)