..... I don't fucking get this game. Is the point, NOT to have sex with all the girls and just stay committed to one? Because the game sure the fuck is punishing me for doing the thing I though you were supposed to do.
The games got a lot of harems, but to form those you need to meet certain requirements. Sasha and Bree are your roommates and theyre the main two of the home harem. If you sleep with 2 girls, who can form a harem, within a week of each other before the requirements are met then there can be a showdown if you are in the same room as both of them, the result is that one or both leave the game.
The games designed with the idea to be replayed, so you experiment learn things, fuck up some etc but eventually start a new game plus with high stats and money and then try something different. If you don't want to learn as you go then I'd suggest reading the wiki, it explains a lot in decent detail.
Personally I think the games pretty fun and worth it but if none of that's what you're looking for/interested in there's always a ton of other games on here that might be more in line with what you're after