Responses
Manjiro (the eel looking for a ring) already proved that dead humans can turn into yokai if they feel they cannot leave the human world. However, I think the house yokai was not a person but a spirit born from the memories left in the house after its destruction.
idk how i feel about that cuz the yokai speaks like a child
i think abeno's explanation makes more sense
I wonder if human spirits can become demons if they have a strong enough attachment to the living and unresolved feelings?
If so, it's possible that the house is actually the mother. I mean, it has all these sentimental memories of the child (and, so far, no mention of the mother who's in some of the pictures). Maybe the house burned down, or collapsed, and the mother died and became the conscience of the house and, seeing the album of cherished memories, she wants it to be returned to her (hopefully) living son.
This feels like another emotional arc, and I'm prepared to cry if any of what I said comes true, lol