Yeah like Haise said, you need to at least complete the main story where the girls begin training with Kiyo for pet play option to appear. Also the library quest triggers in Ai's room at night on weekdays, kinda confusing I know lol（´v｀;）
Thanks this answers my questions I haven't started training quite yet we have just resolved to do so. I do actually have another question how do I find Zara and Charlotte?
I believe it's after you become friends with mio and the story is in ai's room during the day on weekdays, but if your talking about after the story you'll find them at the apartment complex at night
