It's actually really good. It's simple, it's got good original art, and it doesn't take an absurd amount of time or effort to play and complete.
Having said that, a couple critiques/suggestions. While I think the art for the 'mons is really good, I can't say the same for the male figure. He's kinda bland, and since your art is mostly clean sex, there's not much appeal. And his dick is dawn horribly sometimes (particularly for Weedle), and why does it get so thin for Abra? It would be more exciting with a better-felt sex scene, rather than the idea of one. It's not just about "oh, he's putting it in [oriface]" it's supposed to be "aw yeah, he's really getting her!"
With that in mind, maybe you could do animated sexcards for some of the iconic ones, like Pikachu or Clefairy? I noticed the figures are already animated in the bag, although just slightly. As a player, I'd love to see all the scenes animated, with proper facial expressions to match, but I know that's demanding a lot. But just some excitement rather than just a picture. Or maybe you could make a challenge to unlock animated sexcards for them, make us work for our porn, you know. Then just an arrow on the sexcard itself to go between them. Just a thought.
The gameplay is great, just the horniness appeal was lacking. The only minor complaint I had was the unnecessary 1 level when going from 99 > 100. Maybe you could start every 'mon off at level 1 instead of 0? Idk. It just felt like a waste of stamina to use 1/10 of a day on 1 level.
I know you've got a lot planned and several ideas in the comments. It's really a good game, so I look forward to future installments! :D