This compliment might be strange among others - but damn, that music! So groovy, gets in the mood so well :3 Great choice!
You should seriously consider doing more of these(not necessarily this genre ofc) - You have a level of animation matching that of ZONE.
Could easily monetize that I believe.
Some things you could work on :
Your own voice actresses
More fluid animation(less in and out, there should be a sense of "impact" behind each thrust like if you feelin me, moar titty bounce and booty thrust waves haha)
Perhaps some in-game little text bubbles with some naughty lines during the interaction?
More interactiveness?(Smack dat ass! Pull that hair!)
More randomness(randomly changing expressions, head bangs, doin stuff with hands etc, anything to make it look less artificial)
That's all that came to my mind straight up.
Hope that helped, highly anticipating future parts.