Not gonna lie, from the concept I was expecting some weird vore shit, but it turned out to be much more interesting and wholesome. A pleasant surprise.
Just starting out, so I don't know the answer yet, but it seems like Watari has a lot of self-esteem image, and the fact that she froze up like she did after seeing herself in the dress makes me think she might have issues with poor body image.
Very sweet ending, glad they came be happy together.
Still, I think she should seriously talk to someone. She may need to be medicated. Like, avoiding the whole "split personality voices in my head" thing, she seriously seems to be suffering from major depression (trust me, I know from experience).
I'm genuinely curious as to what was going on outside.
My two guesses are some kind of Hyakki Yagyo (When the yokai go on parade), or a Fox Wedding. The first is a bit more dangerous than the second, but NEVER underestimate kitsune
EDIT: Well, I have my answer
I mean, technically, Hellsing started out as a hentai one-shot. The series also repurposed characters from 2 other hentai series he published, Coyote and Angel Dust.