Wildcats are always trying to ambush you, so you see an empty screen at first; pick any non-run option to start the fight, and make sure that you have male partners enabled, as you must win through lewd attacks (winning just once is enough). Or you mean that you don't get even that? If you meant that you want to force the game to spawn them, then it's not possible. There are two possible enemies (three after starting one quest), and game just rolls randomly.
As for the enemies on the underground arena, they're unlewdable (excluding Lin Lin).