MoolahMilk. Hey. Just wanted to let you know you've created a pretty great game. Your interface, puzzles and character models are all really slick and you should give yourself a big pat on the back!
As a huge fan of the impregnation/pregnancy genre, I'm really looking forward to how this will be implemented in a game of this quality. Given you are probably still planning this out, I'd like to respectfully put forward some suggestions for your consideration.
Firstly, I think the "chase" in impregnation is really important. So, having some girls initially insist on the MC wearing a condom or pulling out actually adds to the whole situation. Having to convince or trick the girl to stop taking contraception and go raw is part of the fun.
Secondly, I think the "probability" aspect of impregnation adds a layer of playability to things. Circle Green Curry's "Perfect Lover" has this system in which each girl's fertility differs day-to-day. This is a fun, simple system as it gives the player incentive to focus on girls on specific days. It also allows for situations where a girl allows creampies on "safe" days, which really encourages the player to go to town and surprise her.
Finally, Japanese games often have some sort of simple "internal view" for creampies (potentially toggle-able) and this really adds to the whole impregnation thing. Showing the womb slowly fill up and relating this to the probability of impregnation ties it all together.
Again, thanks for a great game and hope I wasn't being too presumptuous with my suggestions. Whatever you do, I'm sure it will be great.