The author has a weird habit of revealing a tragic backstory after every female villain is exposed. No concubine is truly evil in this world, which goes directly at odds to the genre of both the story and the game. Every time they do something wrong or morally dubious they are doing it for their friend, their child, or their own misconceptions about what actually occurred. The only exception to this rule is the character the MC is possessing, the "villainess" of the game who effectively stops existing the second the series starts. Even her own misdeeds don't really come back to her, at all.
Interestingly the same is not true of the male characters in this series. They are allowed to be brutal, self-serving, and evil, and are actively glorified for it. The two male love interests are both effectively subtler yanderes whose only interest is "loving" the main character, which effectively manifests as an obsession with owning and controlling her rather than any level of mutual respect or interest.
The only character who gets a significant portion of screen time outside of the disgusting male leads and Yona herself is Lili. Lili is a character with potential, being the narrative opposition to the mc in the original story and having her own secrets. Unfortunately the author quickly retcons any of her antagonistic feelings and actions, and instead shunts the character into the role of plot propellant and narrative expositor. Lili no longer has any real purpose and only serves to move things along or be useful to the mc.
Worst of all is the MC herself. She is a genuine idiot, both intellectually and emotionally. She is constantly pulled along into the conspiracies of the other concubines and the two male love interests and never actually acts on her own. She is a reactive character and her reactions are always stupid. She has seen the murderous and cruel sides of both male leads but is still deluded into thinking they have genuine love for her and swoons constantly. Even the few times she gets one up on a conspirator against her, it is always propelled by someone else. Someone else reveals the problem to her and presents a solution, all she has to do is act along with it. She has no real personal motivation beyond escaping the game, and even that she constantly ignores for her whims to be horny with the male leads and to play nice with concubines who theoretically want her dead. I might be more okay with the naive innocence if this was still early in the story, but at this point she has been living in the game for literal months (if not years!) and is still as useless and refusing to be proactive as ever.
I hate this series and regret reading it. It constantly taunts you with the concept of it becoming better and never does, and at times even seems to spite you for thinking it might.