I’m too lazy to read it so anyone give me spoilers? Why is she a fake sister? What type ...

I’ve been reading this not so often that I don’t even know the character’s names lol but from my recollection…

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- She’s a fake sister cause they brought in the MC to pretend to be the missing sister of the black hair guy which is the ML(?). They not related in any ways even tho she does look like the sister.

- MC is scared of the brother and uncle. Afraid of being found out and not need for her role and end up killed or tossed to get r-ped. The brother has conflicted emotion about her. I think he knows that she’s not his sister because she doesn’t kill animals/people and her eye color is wrong. He’s not 100% sure who she really is though. I think he likes her deep down but don’t know why yet. From novel spoiler he got hard ons from her but the webtoon didn’t really show that. It’s really vague.

- I think when he first told her to do something naughty she was offended and left but then asked for gold coin next time she saw him. I guess he thinks she wants gold to do it. He thinks she was a prostitute and she thinks he is thinking that because his uncle told him he found her at a brothel after getting caught that she’s not the real sister. Maybe she did do stuff for coins before with him but the webtoon didn’t show it but the novel did

Spoilers only from manhwa
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FL is the fake sister and a princess from another country. Her whole family was killed and she's the sole survivor. She was hiding her identity in brothels and trying to survive. She's brought to play the missing sister in the Archdukes family by the uncle. Uncle wants to use her to dismantle the family and start a war basically bc he has craaaaazy beef w the ml.
She looks like ml's sister but she ALSO looks like (and IS) his childhood crush / first love / fiancé (? I don't rmbr) so.. weird af over there! He knows she's not his sister but doesn't know for sure who she is so he wants her but more like he wants to Own her. He does attempt to pay her for sex and generally degrades her often. He pierced her ears bc he thought she'd look pretty w a jewel LOL
He is her first love / whatever but she doesn't know that. She's scared of him but also she thinks he's sexy I guess?
Overall they're a mess and a half. Nothing happens. He did jack off to her handkerchief and they did have sex recently but they just talk in circles around the point.