The setting makes sense only if you aren't able to read, and the romance is terrible. The review below contains info about the first three chapters, which are also summarized in the synopsis, so I won't count them as spoilers.
The premise is ridiculously forced, as if the author didn't even try to create a believable setting. While writing his will, Charlotte's grandfather properly gave her the title by mentioning her by name, but then gave everything else to her naming her as "Albert's daughter" (Albert is her father), using extremely vague language despite knowing that Albert's hedonistic tendencies could have easily led him to conceiving more than one daughter (which they obviously did).
But wait, it gets better. In chapter 3, it's actually proven that the plot must have been written by a brainless ape.
The late count's will clearly stated that all his fortune would go to Albert's "daughter." Which means Charlotte wasn't the only one entitled to the vast inheritance. As long as he can present a daughter of his, she would be eligible for the inheritance, allowing him to snatch it later. So Albert tracked down all his illegitimate daughters from the past. But the late count was aware of this loophole. He predicted Albert's move before his death and located all of his grandchildren, paying every last one of them to sign a waiver to their rights to the inheritance.
The above is a direct quite from the story. Am I GENUINELY supposed to believe that this demented cretin of a grandfather thought it would be easier to track down every single one of Albert's spawn instead of just clarifying in his will that all his fortune would go to Charlotte? Previously, I thought that the author meant for Charlotte's grandfather to mistakenly use vague language, leading to this situation. But now? Now, it doesn't even make sense, since the fact that he searched for all of Albert's daughters means he KNEW that the vague terminology he used in his will could be exploited. God, it hurts my brain how stupid this is. And every single plot and problem that followed this was just as absurd and stupid.
The romance isn't any better. Literally every single person who's involved in romance just falls with their counterpart at first sight, and every single one of them feels simply forced and artificial.
The only reason I kept reading was the sisterly love, but honestly, it wasn't enough to keep me from dropping this hot garbage. It's actually offensive how illogical and bad this whole thing is.