User blog comment:Kazekage21/Half Demon/Half Humans and Demonic Devil Fruits/@comment-1949750-20120111220950/@comment-4080028-20120112142337

I agree on all points made by FMF here. I'm not going to feel comfortable with demons and demon/human hybrids being a species, as that may cause more trouble than it's worth. However, i've always seen the One Piece world as some kind of wondrous place where strange and exotic new things are always just around the corner. Thus, I find it believable that there would be SPIRITUAL demons in One Piece. After all, Brook was once mistaken for Satan himself after he was sent flying by Kuma.

However, since there's such a huge concern over religion on this site, i'd also like to avoid bringing it up more than it has to be (which isn't saying much.) So yes, i'd accept cursed objects, demonic auras (more in how FMF described it, as in personality or fighting spirit. Or hell (no pun intended,) even simply in behavior,) and evil spirits; but flesh and blood demons may be going too far, as this would slowly turn One Piece into Inuyasha or Bleach, which it is not. This is a story about people (more specifically, pirates, Marines, Revolutionaries, and other occupations unveiled in the canon.)

The way I see it, in real life, demons can affect humanity due to tragic events at a certain location, or even tampering with dark and unholy objects. Hell, there have been cases of people summoning demons as well. So as long as we keep it simple, and not stray too far away from what mythology dictates, this may be our guideline as to how demons would even be able to interact with the non-demonic characters of this series.

...Though of course, not everyone will see it this way, which I don't mind. I just want to throw in a few things to consider before we make a final decision on the matter.