That assumes they have some sort of feeling for the emperor. Remember that most royal marriages were convenience based with the girl most times never speaking a word to her husband before the wedding. Hell, there would be times they wouldn't even get a say. The emperor could spot them on the street and decide he wanted them and that was that, as long as the girl was not married she could not say no, even if she was engaged. Sometimes even if she was married, it would be even worse, because if she caught his interest, often he would request her to her husband and the husband either could not refuse, or would use the chance to gain political advantages. And again there is no saying no on the woman's part. That is why I don't consider harem settings as actual relationships in any of these stories. If one of the parties would rather not be involved in the relationship if they could help it, it's not a relationship for me, because there is no real consent going on. Same with stories about child bethrothals. No real consent, no real relationship.
I like this manhwa, but the only thing I dislike is that the Emperor has a double, and that double defiled the other concubines, thinking that was their Emperor, their supposed husband. The double slept with his (Emperor's) concubine, and then one of them even got pregnant. Bro, that's not right at all.
What if those concubines know the truth? Then they will die a horrible death; after all, women in that age value innocents and reputations. Please correct me if I'm wrong.