"River Where the Moon Rises" retells the romance in between Pyeonggang as well as On Dal, who are characters in a classic Goguryeo folktale. Pyeonggang, also referred to as Yeom Ga Jin, is an enthusiastic female that dreams of becoming the very first lady to lead Goguryeo, and she makes use of On Dal's sensations for her to achieve her goals. Kim So Hyun will play Pyeonggang, that is birthed a princess as well as increased a soldier. She is clever and rational. Ji Soo has been cast in the role of On Dal, a peace-loving, pure guy that goes against his concepts in order to secure Pyeonggang. Kang Ha Neul will play On Dal's father On Hyup, the chief of the Sunnobu people and a basic for Goguryeo. Lee Ji Hoon will certainly play the elite general Go Geon, who is perfect in every means. For the first time in his life, he longs to make Pyeonggang his as well as studies an extreme defend her heart.