The emperor does eventually reveal that he has some feelings for Navier. After Rashta gets preggo, he still protects her while believing that Navier can fend herself off bec you know, she had the training to be empress and yada-yada. It's also revealed that when they were kids, Navier and Sovieshu had some kind of diet that would keep their figure perfect as royal family. This ended up with both of them getting way too hungry growing up. Around this time, Sovieshu* found some cookies in his mom's room (the empres that that time) and he decided to share it with Navier. Turns out those cookies were a present for a conubine and was drugged with some abortive agents that can cause infertility. Despite his feelings for Navier, Sovieshu still wishes for a family and reeeeeeeeaally, REEEEEEEEEEEEEEAALLLY wants a kid. Navier has expressed that she WILL NOT adopt Rashta's unborn baby and has no plans to do, so what does our super genius emperor do? You guessed it, divorce!
Yes, he plans to divorce Navier and put Rashta as empress for a year, just enough for the kid to born and be a part of the royal family. He also plans to remarry Navier after said year bec he knows that Rashta ain't empress material, so he plans to use her ineptitude as a means to denounce the empress title and bring back Navier to his side. Fortunately for Navier, she gets does get married to our beautiful newly appointed king of the West, Heinley. Now this is where it gets stupider, Sovieshu gets upset over Navier decision and ends up locking her on her castle bec he doesn't want her to leave him. Soooooooooooooooooooooooooooooo....
Also going for Rashta, yes, she's definitely not a villain but I also think her gullible-ness and eventual greed is her downfall. After Heinley's friend keeps whispering to her ear about being empress, actually it was his idea that she become the empress, Rashta gets haughty and starts to behave rather... terribly. It's very hard to describe but basically, her actions starts to play a bit more... tactless? Anyway, since she doesn't have proper training, her actions are all fueled by two things:
1. Survival of her children (from her ex-lover, Allan or Allen and from Sovieshu )
2. Her survival so she doesn't become a slave again
Unlike Navier, Rashta is quick to play the victim, whereas Navier takes every criticism thrown at her with pride, this attitude of Rashta is very unlikely for a noble, not to mention as empress. Perhaps for the common folk and slave, it works but for nobles, especially royal families, their pride is definitely very important. During the divorce, it worried Navier that Rashta was behaving poorly, unfit for an empress so she tells Elgy, Heinly's friend, that to inform her immediately if Rashta's actions as empress causes the people of the Eastern empire problems bec regardless if she's no longer the empress, she's still the queen.
So to summarize, Rashta and Sovieshu are both fueled by their selfishness and doesn't seem to care whoever they hurt along the way.
1. Sovieshu - wanting a child despite hurting Navier
2. Rashta - the survival of her children plus herself