Are we actually entering a deeper plot? Things just got interesting!
It looks like the black cat is being set up as the villian. Assuming she was the girl hugging Marron/Ogino in the brief flashback, where were her cat ears and tail when she was young? That could mean that 1: she’s faking being a Catalus for an unknown reason or 2: Catalus Syndrome can be passed on to normal humans? Maybe she became a Catalus because of extended contact with Marron/Ogino and suffered because of it? That would explain Marrons words to Yuuki during the festival.