I'd find it sad too because I would want them to go to heaven then and there. It's as if her father is saying that he has unfinished business with her on the pudding incident. Jeez!
this raises many questions.
are the spirits dead creatures who changed after sticking around the mortal plane for a while?
the cat creatures would support this theory
could mieruko's dad eventually be turned into one of those?
are they the manifestation of ideas and concepts — e.g. the store monster
there's really no support for this other than my ass