I am mostly worried about user flow and how players will get to that point. We have a system for girls getting more familiar with the players. So how we would go from that to what you want is the question.
Well perhaps a caertain level of familiarity is required to favourite someone And then your favourite has their own levels of bond until they can be a pet. Again, you don't have to worry too much about my wants, I just like throwing out ideas I like and see what makes sense for you~