Reserved in case.

I wonder if the Kuchisake-onna is an assassin of some sort or just a wandering sociopath?

Either or I wouldn't be surprised if the little sister milady's little sister (mechanical buddy universe) might try to hire her to get rid of her dead sister's body double milady (mechanical buddy universe) since she's so obsessed with destroying her.

Making a deal with a devil is something I don't think is beyond her.