the art is phenomenal! anyways, I've read some spoilers, and garan was not taken as jahyeon's concubine, but jahyeon did indeed cheat on soru. multiple times (geez, i really hope the artist don't include the sex scenes). soru finds out and feels sad, but she, as a doormat, doesn't do anything about it. one day, the unsuspecting jahyeon is going to go out as usual to garan, but soru tries to stop him, saying his life is in danger(it was true), but jahyeon doesn't listen, and i assume he says pretty insulting things to her, before he goes to garan only to find out it was a trap. he almost dies, but is saved by yato by soru's plead and his injuries were healed by soru and it was at this moment in his semi-conscious state, he realizes he loves her. he wakes up and wants to see soru, but she's gone- she disappeared together with yato. soru does not lose her memories, but since yato is the only one who was kind to her without ulterior motives, she falls in love with him. they have a happy ending, whereas jahyeon, who became the emperor and married garan, lives in regret for the rest of his life.
Heeran Love Song