Don't listen to the people crying over the "back-button".
Never cared much for that, anyway. There are saves for more important stuff, that's enough.
But lets talk a bit more about the game.
I mean there a re a lot of games like this, and i think it's a good thing if you'd take some ideas from them, for example a quest-marker of some sorts. A journal, if you will, where the player can check progress of the different characters and maybe even get hints. The next big point is consistency. If you have a character, use similar looking models, or even more preferably, just one model. There are a lot of models that offer a vast variety of scenes, pictures and videos to chose from.
For example yandex(.com) is a good place to start looking for specific content. If the model doesn't offer that specific scene you had in mind, maybe write one for something the model offers. And, at least in my opinion, choices are important. Give the player the feeling that he's the one to decide, especially when it comes to incest-stuff - from what i've seen so far - players really enjoy having multiple options and decissions.
Some people kind of dislike it when there's real porn in games like that - But a lot people really don't like it if there's basically a new model for every scene the character has. Myself included. With more consistency on that part tho, most people will enjoy it.