don't know how likely a previous owner would be (assume she wouldn't be older considering the mansion is run down unless it just 'turned bad/dirty' from negative spirit energy but wouldn't be surprised if some was some like "occult enthusiast" or sothanks for the translation!
new character looks oddly like non-chan... and seems to know about the mansions properties beyond the stories? i have a feeling she could be the pervious owner of non
I think Akari's parents just sort of gave up on trying with her tbh. Like, either they or the girl's parents must have saved her out of the house and away from Akari. And we know that Akari hasn't changed much from then, it's safe to say that her parents knew about her twisted personality and they either failed to educate her on being normal, or they just gave up on her.gurl where are your parents, you'd think they'd tell her to do things in moderation
but dang lol early yandere blooming