as a side note, is "sunset" meant to be a parody of sunrise?
it occurred to me afterward that the anime title might be a reference to powerpuff girls Z, although that's a lot older than 2017. highly recommend watching the transformation sequences from that, they're awesome.
also yeah it wouldn't surprise me at all if this was itou hachi contrasting her adult and child selves. it's honestly a significant thing in her work to have a huge contrast between the complicated ugly reality of adulthood vs the pure-hearted earnest enthusiasm of youth. you could probably write a whole analysis on it if you wanted to.