[Freakman]

Wow. Just finished reading through Minagoroshi.

Spoiler:

[Big spoilers removed]

And finally some suppositions about Satoko/Satoshi (which may be obvious though, but then I'm pretty slow)
Satoko has gone to level 5 once. Which means that if she didn't commit suicide, she at least committed a violent act.
So she must have killed the aunt. But there are some couple issues with time tables (iirc, Satoko was at the Matsuri ?), but it sounds the most likely. Considering the Rika-Satoko exchange after Rika tells the truth about the Syndrome, it sounds believable.
After that, Satoshi tries to cover for his sister but as a result gets suspected by the police (I'll assume he was at the scene).
At this point the commando intervenes, pulls up the insane-gets suicided-hannin and onikakushies Satoshi (because he had seen Satoko kill the aunt, or because he was suspected by the police ? Had Satoshi not been suspected, they would have onikakushied Satoko ? Although that's doubtful because at that point research was still ongoing I guess. So they had to onikakushi Satoshi to cover all tracks.
But the one point that doesn't work with this theory, is that Takano refuses to reveal whether she killed Satoshi or not.