What if Umineko When They Cry Episodes 1-4 and Higurashi When They Cry Sotsu/Meguri are one and the same?
https://tvtropes.org/pmwiki/pmwiki.php/Characters/HigurashiWhenTheyCry
https://tvtropes.org/pmwiki/pmwiki.php/Characters/UminekoWhenTheyCry
Bernkastel’s Letter(https://07th-expansion.fandom.com/wiki/Bernkastel%27s_Letter) seems quite uncharacteristic of Bernkastel and more like Rika Furude(who has infact called herself Bernkastel) desperately trying to get Bernkastel(who does match the description of the receiver of Bernkastel’s Letter) to help her deal with Beatrice.
Furthermore Eua like Rika seems to know Lambdadelta/Vier and mistakes Satoko for her in Sotsu and Meguri’s first few Episodes/Chapters.
Sotsu according to the writer of the Higurashi and Umineko Visual Novels deviated against the outline he gave the Anime Writers of the Story so the events are not to be taken as Canon except where things agree with the Higurashi Meguri Manga.
I suspect that Eua is Rika herself empowered by Lambdadelta(a Clone of Satoko or a lookalike created by Nomura along with Takano Miyoko’s Adoptive Grandfather who constantly mistook Miyoko for Lambdadelta leading to her taking on the Japanese translation of her name Miyo) into both rescuing Maria Ushiromiya(turning her into Hanyuu) and giving Satoko Time Loops and that Lambdadelta is infact carrying out the Hinamizawa Disaster herself(with Nomura ordering a cease on all work on the Hinamazawa Syndrome) and is forcing Satoko to set up the board game using the legend of Beatrice in hopes of forcing Rika to buy Bernkastel.
How does Satoko know of Beatrice? She is Ange Ushiromiya who along with Battler was adopted by the Houjou Family with her Adopted Mother being Aunt Eva herself who following her husband’s demise reclaimed the Ushiromiya family name and let Ange be taken in by her In-Laws.
Lambdadelta of course uses threats to keep Satoko in line after Rika gains awareness of Lambdadelta being separate from Satoko(some time before she sends Frederica Bernkastel’s Letter to Lady Bernkastel).
Satoko/Ange after ditching her usual identity to become a Red-Haired Girl from nowhere due to the stress put on her by Lambdadelta eventually gets drunk enough on Lady Bernkastel to expose her identity(mostly because Lambdadelta is posing as Satoko to the public).
Rika and Hanyuu eventually captures Lambdadelta(after Episode 4 gets Satoko killed before Rika) and keeps her in an unbreakable seal using Bernkastel to keep her occupied with Hanyuu monitoring her while Rika(given a means to preform 3 more loops) lives out her own life until Adulthood upon which Nomura/the Real Beatrice makes her move upon Rokkenjima certain that Rika can’t stop the 10 Twilights of the Witch’s Epitaph from happening.
Cue https://07th-expansion.fandom.com/wiki/Higurashi_no_Naku_Koro_ni_Rei_(manga).
That’s when Episode 5 happens and Rika gets Hanyuu/Maria Ushiromiya to go over her recollection of things leading up to the crime(with Hanyuu being the detective AKA Erika Furudo) ultimately proving that Kinzo was dead before the Massacre happened. Episode 6 is Rika and Hanyuu finding out that Satoko/Ange despite what Lambdadelta told Rika did go to the same fragment as Rika despite dying before her.
Episode 7 is likely Rika, Ange, Maria/Hanyuu and the suspiciously Beatrice-like Une(https://07th-expansion.fandom.com/wiki/Une?so=search) trying to figure out what is going on with the Rokkenjima family.
Une firsts reveals the motive and identity of Beatrice before everyone else learns from Maria that Ange’s parents were responsible(not hard since Maria was directly present before Rika empowered by Lambdadelta turned her into Hanyuu).
Episode 8 is Ange getting confirmation of her Parents’ crimes falling into despair in the process(after failing to die due to the Looper powers being permanent) and along with Rika is about to reveal the contents of Eva’s Diary to world only stopping when she figures out that her brother is still alive and(as shown by Ciconia When They Cry having Doctor Nanjō among the Three Kings) that her family can be revived the same way Rika revived Maria as Hanyuu.
The Trick Ending is about Ange and Maria figuring out that Nomura and Une are Beatrice herself and cornering her before killing her(along with whatever accomplice she has with her).
The Magic Ending is a catatonic Battler being restored to his old self and reuniting with his family as Ange builds a physical Golden Land on the ruins of Rokkenjima.
Of course these happy days are not to last(and I don’t mean the hiccup that is Umineko episode 9 where Rika tries to bring back either Ange’s Stepmother or Rika’s Biological Mother) as Lambdadelta/Vier Dreissig desperate for a constant acquisition of Bernkastel hooks Rika up to Sekhmet whom as all readers of Egyptian Myth know like Lambdadelta is only kept under control by Alcohol(with Rika/Miyao Mitake willing to resort to drinking Bernkastel/MIYAO till she passes out/is deleted to stop her). Cue Ciconia When They Cry.