Nareul Saranghaji Anneun Geudaeege

Ages ago in a land of myth and legend, a young girl called Rose stands tied to a stake, awaiting her cruel fate as a sacrifice to the sea serpent known as Leviathan. That is, until a dashing hero suddenly appears to defeat the monster and save Rose’s life. Eternally grateful, Rose becomes devoted to her rescuer Mikhail, who is the demigod son of the moon goddess, Diana. She joins his party of adventurers, but soon comes to realize that her savior may not be as noble as he seems…

(Source: Webtoons)