The character design is quite problematic. I'm really struggling to understand the FL's mother and brother.

----------Mother----------
Regarding the mother, she's been blaming the FL for her own negligence in supervising her small children, which resulted in a serious accident when the FL was just 10 years old. It's absurd how she continues to openly blame a child for 20 years when it's obvious that the adult should take responsibility. She doesn't just do this in their personal life, but also in their work life, going as far as finding reasons to sue her own daughter, which could harm their family company that's publicly traded on the stock market. And all of this is happening right under the noses of the FL's grandfather and father, who are much more rational and surely wouldn't want their corporation's reputation tarnished. The whole situation is just so unrealistic and absurd.

----------Brother----------
As for the brother, it's unbelievable. His wife deceives him into marriage and even has a child with another man while they're married. Then she flees away with money of her husband's family, only to return after being abused by her child's biological father. Despite all this, the brother unquestionably welcomes her back with open arms, and still loves her illegitimate child as if the child is his own. It's like he lacks any capacity for learning or judgment. It's hard to trust someone like him to run a company at an executive level, yet he holds a high-ranking position in their publicly listed company. How is that even possible?

----------Female Lead----------
And don't even get me started on the FL herself. She gets kidnapped by the villain in a car. And when the ML catches up with them after a violent car chase, succeeding in rescuing her while he's injured, she complies with the villain's gaslighting to say that she voluntarily follows the villain, then she willingly gets back into the villain's car to be kidnapped again. The reason the villain gives her is that if she doesn't go along, the ML will realize her illness is worsening, causing her to mistake the villain for the ML. But later on, the ML still has to break into the house where the FL is being held captive to rescue her once more, and she still has to tell the ML the truth in the end. It's infuriating how easily she falls for such manipulation, especially considering the ML already knows about her illness and its progression.

----------Toxic love----------
Let me address the ML's love for the FL as my last point. I find his renewed affection for her perplexing. While his initial love before their marriage is understandable, I fail to comprehend how he could still love her after enduring a toxic relationship. Despite their troubled history, she continues to resist cooperation, vilify him, withhold her true feelings, and maintain emotional distance. It appears to be a very one-sided effort, devoid of reciprocity. His affection seems solely driven by blind devotion, without any tangible reason or justification. Their past history of love before marriage doesn't seem to influence his current feelings, and the FL's behavior offers little to warrant his continued love. In essence, it feels like he is merely serving her as a servant of love. Such a dynamic doesn't foster a genuine and sustainable relationship in real life, though.

The story's irrational elements are so frustrating to watch. I keep going with it until the end because I'm a fan of the lead actors. However, while the FL's acting is passable, it still comes across as quite stiff to me. I've seen her in 3 series, including 'Descendants of the Sun' and 'Fight for My Way,' and her acting seems to be consistently one-dimensional, and not even the best version of the character she's portraying.