A friend of mine directed me to a porn game currently in the works called Breeding Season
(note: link is definitely NSFW) and would dig an RP based on/inspired by that, with maybe a hint of Harvest Moon/Story of Seasons.
Basically, a brother and sister (or just one guy or one girl, if you'd rather) inherit a farm from their parents that was used to breed monsters. Unfortunately, the farm had fallen into a bit of disrepair since their parents passed away, as well as racking up a considerable debt. Also, the empire frowns on the practice of breeding monsters. Since the farm is located on the frontier, though, they can't actually ban the practice of monster breeding. They can, however, impose taxes on it. So it's up to the new breeders to get the farm up and running and to stay a step ahead of their debtors.
The monsters, in question, will certainly be bred with one another...but while they're still working on getting the farm on its feet, the breeders may need to get down and dirty to produce more monsters.
As to the monsters, themselves: they are sapient humanoid creatures that roam the lands. They are a reflection of the base desires, and they become more desperate to fulfill those desires the more the people around them repress their own desires.
Below are some pictoral references and ideas for characters we could use in an RP like this.This is a good place to look up info on the game and characters.Milking a holstaurusHolstaurus/Catgirl breedingMore Holstaurus/Catgirl breedingBreeding catgirls, harpies, and holstauri yourself