May 2 2009 03:19 PM Well from what I can asume from the series is this. The Hinamizawa Syndrome is something to do with the location of the village. I think might might have something to do with the swamp nearby though. Also, since it was mentioned that if Rika dies the people will go beserk because she is the main carrier that controlls the town.
So if you look at it that way you could say that this has something to do with the Fruude lineage if that's the case. Also, it could be that since Hanyuu is an ancestor of Rika's it could be that the family was crused since they have the bloneline of a demon running through them. Not only that, but I'll bet that there were a few demons that were fairly passive as well and that's probablly why they say that people were demoned away though.