Actually I read about Takano in the game thread of this forum and the part where people where discussing about the minagorishi-hen chapter.
Unless I have misread, wasn't Takano supposed to be a victim turned villian? Not by the virus but from the people that was once using her.
Unless of course Takano is a character who is based off on old-school RPGs and old-days shounen anime where you have this villan who is evil for no other reason then to just be an evil presence to keep the plot going.
But since Higurashi is about characters with complex difficulty I doubt Takano is one of those "Because she is born evil" characters from old-days RPGs, that would be too simple.
The game thread here also mentions someone by the name of Koizumi who is somehow related to Takano. This guy isn't mentioned in the anime nor in the TIPs of this thread so I don't know who exactly he is, My guess is that Koizumi is a scientist like Takano and that they are reasearching something dangerous.
I don't know how Koizumi passes away which he eventually does. Takano took it really hard. Also at some point the other scientists decide to use Takano as a specimen. Now unless she has absolutley no connection to Hinamazawa then I don't understand why she would have a grudge against that population. My guess is that Takano probably is a decendant from that village who's genetic properties have gained the interest of the right-wing extremists.
I think the specific page of the thread would be here:
http://forums.animesuki.com/showthre...t=26475&page=9
I think that if you also go back a page or two or forward a page or two you will find that Takano was forcefully quarantined in a medical building and was subject to cruel experiments.
Takano's hatred is trully strong, I would like to know where it came from. She doesn't seem to show regret or guilt like the protagonists do. Something other than the village disease must have hit her hard.