I remember this manga! YESSS! This author works are a real hit or miss for me since he tends to go overboard with the crazy. But this one was pretty good for the 8 or so chapters it lasted. The art suits it well too.
I think it's definitely meant to be humorous. So it's not as scary as Itou Junji's other works. To me, the characters here are more along the lines of Souichi. But much more evil .
Lol I don't know if we're supposed to ship them or what. But he is so dad-like that I find it really hard to see it that way.
Btw I think they meant that it's like they're grandfather and daughter, not actually are.