하백의 신부 (Bride of the Water God) Vol 1-23 by Mi Kyung Yun

Soah is a girl from a small village suffering from a long, devastating drought. In order to appease the Water God, the most beautiful girl from the village must be sacrificed. Soah is chosen to become Habaek's bride, but instead of dying at the hands of a monster, she is unexpectedly rescued by Habaek and brought to his Kingdom.
As Soah learns to live in a strange new world filled with gods, she is caught up in various intrigues surrounding Habaek and finds it increasingly difficult to know whom she can trust. In the midst of such trouble, she finds she has fallen in love with Mui, unaware that he is the true form of Habaek.