I like how ambiguous that last panel was.
Was there some kind of accident and the kid was the only one who survived? Did he have to live on the streets and that's why he looks so neglected and maltreated?
Or were his parents abusing him and the youkai killed them in a fit of karma? It would make sense why they died by rain if that was the case given the situation.
Or maybe the kid was already dead and a spirit after some case and she didn't realize it? That would explain a lot, but there's also the idea that he wasn't dead in the literal sense, but dead to the world because he was ignored and neglected for so long that he had already "died" in a sense a long time ago, and he can only truly live in the world of the spirits.
A lot of interesting possibilities all from a few panels. Good writing at work.