I can imagine their future convos
Her: I'm going to wear this dress!
Him: If you do that I'm getting exorcised!
BTW, that's a cool monster type I never heard before. Some kind zombie human of lingering will that forcefully
Isekai's himself into other people's bodies, memories, and souls killing the original host. Not like a ghost, where the original primordial substance is unaffected in the body.
My bet is kitsune shrine maiden or just the shrine maiden. That's why the gift boxes were shrine offering things.
What I'm saying is that instead of exorcising him, she boned him.
what if the author didn't think this far and you just cooking up lore for him?
Aren't Shrine Maiden required to remain virgin? Or they lose their power or something?
Also BONED him.