Regarding your question, though, I learned about the two rikas through the TIPS that were on Animesuki. Keiichi’s father saw three children play with each other, among which there were two blue-haired ones. Why don’t we see the second blue-haired girl anywhere, that’s probably how the two of them merged at some time, or something similar.

The fact that there was no gas is simple, as the series sortof explained that. People wouldn’t really be able to fix volcanic gas with concrete, and for some reason, Keiichi and Rena survived. If the entire village was felled with volcanic gas, it couldn’t explain how they survived. If it was, in fact, a cover-up, and the disease was instead awakened, you can explain them. Keiichi was unconscious when he survived, so the disease couldn’t have made him crazy. Rena, meanwhile, was actually cured, so the disease had no effect on her.

I have an answer to some of these questions. Rika’s little friend’s name is hannyu and she is the one who turns back time for Rika. She is supposed to answer more questions when she appears in the second season. Takano IS the one behind all this. She did everything. The killing and crap. I dont know how yet but I know. Irie, I have no clue but maybe its because something happened with satoko because he loves her. The last question about two rika’s, you see in the anime how keiichi was seen at the festival when he really was sneaking into the festival shrine, rena was seen somewhere else when hiding when she couldnt have been at two places at once, and Takano was dead before the festival in the fifth arc but Rika, Rena, Mion, and Keiichi were talking to her anyway. Somehow, there has been copies of people. I dont know why. Anyway, how do you know there might be two rika’s? how do you know already that there was no gas? how did you figure it out? please let me know. www.LOLnessblog.blogspot.com please comment

Here are my thoughts on some of those questions:

“What does Rika’s little friend have to do with this?” and “Are there possibly two Rikas?” — Here’s what I think. Rika’s friend, Hanyuu, is actually Oyashiro-sama. I really thing that this could be it because according to the game tips at A-Suki, Rika is the reincarnation of Oyashiro-sama (http://forums.animesuki.com/showpost.php?p=601921&postcount=64) and I believe that Hanyuu is Rika’s Oyashiro side, which is why she looks like Rika. This would also explain why Rika can only see here, which was shown in the tips. Anyways, I think that Hanyuu will have a big role in the overall picture of things, considering the focus that she and Rika have in the OP & ED.

“And where does Takano fit in this story?” — Your guess is as good as mine; she has to have some idea of what is actually going in Hinamizawa.

“Why did Irie commit suicide?” – I believe he was actually murdered because he found out about the virus or something like that. He probably discovered something he shouldn’t have.

Not at all; Death Note had them.