Ello Nami! (Slight spoilers ahead) I certainly love your series, you did what Zootopia did before they did it, using both prey n prey and angel n demon(even though that one is not in the main story line) you go against racism in both of those lines. I wasn't that fond of Delicacy cause it wasn't right that it wasn't considered how Mochi would feel about any of that by Treat. Other then that the series is amazing in emotion and cuteness and showing off real world problems. Although I havent been able to play this 4th installment to the series cause everytime I click launch it says something about direct X audio which must have something to do with the game sense there is no such thing on my computer.
oh, directx is a program that comes with windows, i think yours just needs to be updated or something? very strange that you could run the other games and not this one though... sorry i can't be of more help, hope that can get figured out!