Looks like the author is doing everything exactly the same as in the pornwa. Differences are so minimal it's not worth a mention.
So if you want to know a bit more about her...
The BF situation is kind of a let down. She has a 3somes with MC and FMC, and then after MC leaves for work she and FMC stay in bed and talk about her. FMC tells her she is banned from sleeping with MC for 3 weeks, so she can sort her feelings.
She gets so horny after 2 weeks that she can't even walk normally lol So she jumps MC one day and then tells him she broke up with her BF. We don't even get an explanation about it, did he cheat or not, nothing...
After they have sex we find out she has fallen for MC for real. She asks him if he wants to marry her, he declines telling her his wife can only be one girl, his GF. She asks can she be his 2nd wife, he is happy about it but the law doesn't allow that. She then replies in a low voice that he can't hear "we can always go to a different country" (foreshadowing???)...
It's worth to mention that there is a CEO type of guy in the shadows investigating MC and his Harem, but since it ended no idea how it would play out. Don't know if this was her Ex or someone else, this part is not translated. I'd bet it was MC/FMCs Dad, he looked a bit older, but who knows.
