I also congratulate you on a solid first effort.
I don't mind the "porn-ish" aspect of it, but the one thing that would have been relatively simple to do, in terms of gameplay, was to make some of the paths exclusive. Having sex with one character didn't preclude having sex with another, and it probably should have.
In a more complex game, with more difficult "puzzles" and such, it can be OK to leave all options open, especially as a sort of reward for someone who can navigate the most difficult possible path through the game. But this is somewhat less a game than it is a story -- there are ways to fail with the partners, but since you can just back-button your way out of any sub-optimal choice, they're not very important -- at least some token replayability would have helped. Just as an example, it would have been more interesting if the key to having sex with the owner was not having sex with any of the other girls.
You wrote some variation into the sex scenes, and that's good, and also something a lot of authors don't consider. Even more variation would be welcome, though I know with graphics that can get difficult. For example, while I liked that not all the encounters were a routine oral/vaginal/anal sequence, maybe one of the girls should have liked her sex a little rougher, since that was quite frequently an option. Maybe one of the encounters should offer anal as a finish but with no good outcome if you attempt it (and this should be hinted at somewhere in the text that precedes it). Maybe one of the encounters should only offer a reward (the "achievement") if you stop after oral, no matter how elaborate the scene that could follow.
The story, porn-like though it might have been, was reasonable, but another important thing to consider might be a more fleshed-out backstory for your antagonists. By which I mean: I would have liked a lot more explanation or justification for why the other men in the story were doing what they were doing.
Again, a good first effort. I look forward to more in the future.