The female lead is unique for a romance story because she is extremely analytical rather than emotional. I really love those moments where she is being deeply critical of her situation and realizing things aren't making logical sense. In the beginning, it seemed like it was going to be just another stupid drunken coincidence that brought her into a relationship with the Emperor, but it delightfully had much more context.
The male lead shows some promise, but could be portrayed more interestingly if more background was given. I like him, but I can't feel a strong emotional connection because many details were kept a mystery. I can imagine writing the character better myself. If the author had shown us flashbacks of his long history of suffering and aimlessness, and what led his fate to the current point, it could have had so much more impact. There is so much that could have been revealed about him, but it feels as if his fascinating backstory was ignored.
The story seems to suffer from petty villains. The antagonists are weak and lack charm. The protagonist's triumphs over pathetic villains don't feel satisfying. This is a common problem with stories. To make a the hero/protagonist shine, it is necessary to give them a worthy opponent/hardship to triumph over.
The side characters are average.
The most interesting part of the plot in this story that sets it apart is a matter of viewpoints.
The Emperor is the regressor rather than the female lead who is the main character and point of view. The idea is great to change it from the female lead to the male lead, but I feel like the author could have taken this curious idea and gone further with it. If there is going to be something unique in the story, a pivotal part of the story, why not put in more effort to make it special and stand out from the crowd?
