The deaths of the 1st 2 Loops matches 2 of the Deaths of the Witch’s Epitaph:
1st Loop: Gouge the Chest and Kill which matches the Fifth Twilight.
2nd: Loop: Gouge the Stomach and Kill which matches the Fourth Twilight.
We don’t know enough about the 3rd Loop to know if Rika got her Knee gouged or if it is really is a victim of the being passing itself off as Oyashiro-sama.
Since Keitarou from the Rei Manga is away from Polaris and is unlikely to be killed by the Angry Mob due to his likely desire to hunt down the Murderer of Rika we might find him getting his knee gouged by Beatrice before getting killed as Rika’s Murderer laments her gambit to catch the real Murderer by siccing everyone on Polaris backfired.
Considering Sakiko’s suspicious behavior and glowing eyes at times I suspect that she is somehow Witch Satoko finding a way into that timeline using Magic in which case the adult Satoko is probably Looper Satoko desperately trying to keep the Witch from causing drama again.
Of course if the Loops are the Twilights then “Gouge the Head and Kill”(the Fourth Twilight) already happened as did “Those who remain shall praise my noble name.”(the Third Twilight) and “Those who remain shall tear apart the two who are close”(Second Twilight) which ironically is exactly what happened at the end of Sotsu: Rika and Satoko were torn apart by the Townsfolk.
That means that Oyashiro-sama/Eua/Featherine Augustus Aurora wrote the Witch’s Epitaph to resurrect Beatrice and is behind the massacre.
Her Mortal disguise’s name Ikuko doesn’t mean Beatrice. It means Nineteenth Person. Beatrice is the 16th and 15th Person(Kanon and Shannon).
Any Detective looking at the Murders of Rokkenjima in Umineko as well as the Witch’s Epitaph would think a Cultist is the Murderer not Beatrice who is supposed to only revive at the Ninth Twilight with the person searching for the Gold being the one intended to commit the Murders on the Epitaph.
The Cast unfortunately go straight to the notion that Beatrice if not someone from the group is supposed to be committing the Murders despite the Epitaph making it clear that someone else possibly even the writer is the Murderer.