A good way to get an S on princess is to go into maiden and look at momo's tips for getting an s on that stage, then use that to get an s in princess. It's worked most of the time. or at least has gotten me an A.

how exactly does one get a background? I keep seeing this cute little demon creatures background that people use and i really want it but have no clue where or how to buy it in game. Is it part of an event or something like that?