So basically (#s "Each story that you see within Umineko is a forgery either based on the writings of Sayo herself or Tohya and Ikuko with the exception of Ep6 Ep7 and Ep8 which likely were never even published. The forgeries written by Sayo are basically her way of venting while the forgeries written by Tohya are his way of attempting to indict Eva as the culprit and are also meant as a tribute to Sayo in a sense")

(#s "And about Kyrie every character within the game cannot do something their irl counterpart cannot. So Kyrie murdering everyone on the island is entirely possible. As for Ange well, the easiest way to understand her story is that its split up between the fictious persona of Ange-Beatrice and Ange Ushiromiya, the latter who we only see a few times in EP4 and who is present throughout all of EP8. Because Ange-Beatrice is merely wish fulfillment for Ange, the scenes involving her are highly suspect. For instance, the battle on Rokkenjima never happened as Ange Ushiromiya never went to Rokkenjima except at the end of her journey")

I can go more into this if you would like