Good game. I have been only touching boobs for the past 2 hours, couldn't figure out how to do the sexy sex stuff, but still, good game
Level up your base stats to unlock purchasable skills in the shop on MC's PC screen (focus dex for 10k and 20k upgrades for mouth and dick respectively)
Check wiki for reference:
https://rec.miraheze.org/wiki/Upgrades
Cheers