For me it is the story line itself and here's why.
- You have the wife where you can boss her around in the shower.
- You have Cassie where you can hint at how she should behave around men giving options to where you can boss her around.
- You have Jane where you can show her who's the man that controls by forcing her to be patient and discreet about meeting you and not caving in when she wants you on that desk.
- You have Lupita where you can literally be her mean boss. I mean, she does need that job and is ready to do whatever needs to be done to keep it.
- You have Nanami where you can take initiative over her when he wants.
- You have Amanda that looks interesting and would fit to need that man around that "takes care of her" though future updates will determine how she will develop, but at least she has potential.
.... And then you have Monica where you are all "mushy mushy" talking around everything and being nice to her and what not. I just don't think it fits if you look at the rest of the characters.
.... And that hair.... what happened to that hair
But like I said, I have fun with the other girls so later on I will skip Monica as much as I can and focus more on the others.