Pretty good start. The dialog could use a little polishing, but isn't as bad as some attempts I've seen.
Right now it is more of a guided experience then a game, as far as you don't have any choices. You might try adding in some options that won't really increase development time much. I mean, sure I'd love a choice of sixteen different positions, but I realize that would take a huge time investment. I mean things like a few dialog options, where you wouldn't have to do any different animations. Perhaps some dirty dialog during the sex scenes (somewhere on the screen where it wouldn't cover the action).
Right now you have doggy style and missionary (the standing doggy for bonus scene, thanks). Maybe a dialog to choose which one you start out with? Maybe she would have different dialog during the scene if you start in one rather then the other. Also, some dialog when he cums inside of her would be nice and could even cater to some additional fetishes, like risky sex.
Then you may do additional changes that don't require a lot of extra work, but could provide even more options. Right now you are limited to anal during doggy style and vaginal during missionary. It would take some time to give the option of either hole in those positions, but not as much time as having to rig an entire scene. This would open the path to even more options like hot-swapping (moving between vaginal and anal) and the choice of where to cum, which in turn open up the option for even more dialog. Dialog is very important in these types of games and it is often overlooked in favor of the animations.
Finally, while I LOVE the design of the game (first person perspective with the blurring and chromatic dispersion around the edges) the current method of choosing things like speed causes you to look down and to the right in order to select the buttons. While that is fine as an option, perhaps the ability to use the mouse wheel to highlight those options (not to directly control the speed, though that is an option) would let you navigate the area better. UI design is also important, but luckily once you get the details ironed out, it is usually set-it-and-forget-it.
If you need any assistance with the dialog, like if there is a translation issue or you just want to focus on the animations and have someone else iron out the dialog, I can lend a hand publico bono. Just let me know.