
Maybe she really loves her boyfriend so much that she can't accept the fact that her boyfriend took his own life. So being prostitute is her way to infiltrate the business/lives of those two chaebols who have something with the death of her boyfriend. For your third question, I think the two guys are both straight. But it is just a fetish for the the white haired guy to join in threesomes.
Plus, I have this feeling that lover of the sister of the black haired guy maybe her boyfriend. Because according to the profiling of the characters, the sister of the black haired guy has a college student lover. But this is just a guess.

Well that's the mystery we will find out as the story continues or perhaps there will be a part in the story that they tried to raise their case to the higher court but due to lack of evidence, the case becomes closed. Unfair justice system sometimes made people go crazy. But in reality, that would be really weird that you will make a big sacrifice to be a prostitute for a guy you loved just to get a justice. Some people make foolish decisions once they are deeply in love.

I think it was the only way to get closer to him, to think that he is a high profiled business man who's also a whore, he won't date her or even entertain her in public. As for her 3years staying with Madam Kim, it was to build her credibility and Madam Kim grew fond of her too so it became easy to grab the highest paying customer. Can't wait for more because art style was fire!
props to the artist i cant even imagine how long it takes 2nd why did she become prostitute cuz her boyfriend commit suicide 3rd why tf are those guy having 3some are they lover