Well right from the opening scenes we get to see Shion dragging an inconsious Mion through the floor on the Sonozaki Mansion; just this scene alot started to give support to what I had then written about regarding that what had happened in Watanagashi-hen.
At that point Shion finaly "cracked" then she switched places with Mion and imprisioned her.
It was clear to me that the person inside the cage was Mion and not Shion.., the one-sama part mencioned before realy gaved my speculations more foundation.., not to mencione the fact that through the entire episode Mion acted realy as a phsyco-Shion.., and when we see Shion in the cage she acted realy like Mion would.., specialy upon seeing Keiichi.., but frightned.
Thus she then called Rika over as to lure Satoko (due to her hatred towards her) and killed her.., after as to not leave any witnesses behind.., she toke out Rika aswell.
Which also fits perfectly regarding on how through this entire episode her anger towards Rika started to grow, as she more and more could not stand to see Satoshi beeing so pushed down on the count of taking all the hits instead of his sister.
I was not surprised upon seeing that Shion did in fact Had love feelings towards Satoshi.., because it was something that I had also based my speculation upon the reasons that made her act as she did towards Mion when she saw that Mion loved Keiichi in Watanagashi-hen.
Something that again, this episode came to prove.
Shion is definitly in love with Satoshi, from the very moment she saw him.., but then to learn on how miserable he was just devastated her.., so she clearly wanted to change that by "fixing" the source of the problem (Satoko).
Which inevitaly lead towards the scene we saw in this episode.
Thing is.., I belive Shion is already extreamly mentaly instable...; and I say this because.., as I saw her beating down on Satoko.. even though the words she was shouting where directed at the cause to make her realise that she was making Satoshi miserable.., It felt to me that in fact the words she was saying where also her inner expressions of hatred and spite against on how Mion had been born first and had been able to live a more free life and in-herit the Sonozaki Leadership.
Which clearly would explain why she in the end, inside had so much hate towards her, as we saw in Watanagashi-hen.
And I guess the same would apply on to Satoko.., for I belive she now sees her as the reason for why Satoshi despizes the Sonozaki family even more..; for.., if she had not made him so miserable, Shion would have never attacked her only to Satoshi in the end enter to protecter her.
Something that.., to Shion now made the chances of him wanting to be with her less possible..
I wonder if this effect will be the trigger which caused Satoshi's death as we saw in the begining of Tatarigoroshi-hen..., as in.. if I can't have him.., then no one will.
All and all the dissapearence of Satoshi, and in this episode we saw how Just important he was to Satoko.., realy explains why Sakoto acted the way she did in Tatarigoroshi-hen.
For depending SO MUCH on her brother.., and then to have seen him dissapear just like that.., clearly she inside is compleatly unstable , and realy went through alot of depression and altough she fought to make it through.., everyday she probably struggles with regret on why such a miserable fate fell upon her.
Something that ended up by driving her over the edge.. as when she became to see Keiichi as beeing cursed and ended up killing him as in to "save him" and make everything good back again.., just as how everything was when Keiichi had just transfered in.
Now lets see if the following episodes continue to give support on all of this or not
As for the "curse" factor.., this episode kind of left me still puzzeled.., but that well.., also has ALOT to do with the last 2 arcs..
The fact though that the possibility that Oyashiro-sama's curse is spread through when someone wishes for someone to die is now VERY possible aswell.., for as we all saw in Tatarigoroshi-hen as Keiichi wished upon other's death.., it happened.., and now Shion doing the same on Satoshi's Aunt..
But since we still don't know "exactly" how Satoshi died.., in this case it might just be coincidence on behalf of Shion's wish.., since what we all saw in Tatarigoroshi-hen was just the "curse's" point of view of the story
All and all the events shown in this episode more or less give a reason to the actions in the 2nd arc.., specialy regarding the Mion / Shion aspects.