The disease is also a nice alternative for the demon-theory. I still have no idea whether the anime will be including supernatural events or not. Still, it does kindof explain what happened at the end of the episode. Mion died at the day the police barged in, so there is a good possibility that she ran away from Keiichi at that time, only to commit suicide at the well because of her disease. Then this means that Keiichi all imagined Mion visiting him the day afterwards, which means that the disease made him stab himself. But then again, this can only be true when the police couldn’t identify Mion and Shion, as the above theory of them switching places wouldn’t add up…

It’s also strange that the demons/diseases in the villagers don’t make these people murder others. It’s also clear that Rena wasn’t infected in the second arc. This also must mean that if there were some kind of disease, there was either something that made the disease inside of her active, there was something that made her catch the disease, or she never had the disease in the first place and Keiichi was the only one who got the disease in the first arc.

If the first were to be true, the disease may start acting when its host is experiencing heavy emotions, much like Pani Poni Dash 19. Like Keiichi giving up to get the doll from out under the trash making Rana sad, Keiichi giving the doll to Rena making Mion sad, Rena approaching Keiichi with an axe in combination with the murder cases making him scared, etc. If the second was to be the case, then there’s got to be someone at which the virus originated, my choice goes out to Mion. She was the one at which the disease started, and spread it to Keiichi and Rena in the first arc, and to Keiichi and Shion in the second arc. If the third option is true, and everything has been happening inside Keiichi’s mind, then what remains true, and what remains fiction? Did the murders really happen, or did they not? Especially at moments at which Keiichi remains calm. Is the disease also taking care of this?

ayyo: Good point. Keiichi’s parents also remain a mystery. During the time that they were away, something must’ve happened to them in order to make them move. Still, why did the date of their absence change? Had it something to do with Keiichi?

Firstly I think that Mion is the one trapped in the cave,and Shion is the one toruring Keichi since the torturing girl often talk of Mion at the 3rd person.Also she knows about the cafe incident in wich only Shion was implicated so it’s Mion who is locked.
But the locked Mion calls her Onee-san,even if we know that the older sister is the heir,so her name is Mion,my therory is that Shion in fact is the true Mion but they exchanged roles since long ago,because it’s safer to have a “bait” when your the head of a yakuza-like family.
Also you’re wrong,Keichi inded becomes crazy,and “Mion” as well since Mion jumped from the 3rd floor,and the vision of Keichi with shion covered in blod and a hammer is clearly a product of his mind,it’s too much.
So let’s sum up Shion is the real Mion she is the jerk,Mion is the real Shion she is the one trapped and K1 becomes crazy again.

Since he becomes crazy again this would mean that this is maybe not a demon who possessed him but something like a disease that affects all town(see the habitants of episode 5 and Rena in first arc),plus there is all that syringe thing,maybe Mion and Rena wanted to give him an antidot,first that the symptoms of crazyness appear its after the hopital…So everybody must have been infected in the hopital!
That lead to that creapy woman,Takano,she is actually a nurse and strangely she don’t die in both of the arc,she just disappear,also the “director” from ep.4 looked a little like her.
Also her photographer friend is kind of strange,he looks more like a military,maybe there was some militar bound between them,wich means that there aren’t any demon in the village but just some kind of militar created disease.Wich makes you understand the “because” of the death of the village chief,it’s just because he knew too much.

Also let’s look a little at the “disease” apparently it makes the person more and more paranoide and it ends up in violent act and suicide.So we can say both the twins and K1 where affected in this act.

As for Rika and Satoko strange behavior I have my theory,maybe they know a way to prevent the desease and they’ve gone to cure “Mion”,a little like Rena and Mion in ep.4. with K1.