And now with that timeline posted in ci-en with some spoilers and all, it makes me see how complex that world is, how the story is bigger than i thought and makes me want even more that prequel game !
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From what i've read, the village of Seraphina is trying to "recreate" a certain Seraphy (Which i suppose is the girl who closely ressemble Seraphina but with kemomimi hair in the prequel game (not true ears, just her hair making it like that) but since the blood has been diluted so much, they can't fully get Seraphy and for now, Seraphina is the closest to her.
Another thing i saw is damn, not a lot of characters would be able to survive the miasma and monsters of the old era, seeing as only like Mina, Iles (Blue haired sorceress which Mina fights at the end of her game), Minne (Daughter of Mina) Lisette (The one who is in the big armor, been modified to be half devil because of possessing bastard in Maid game) and Seraphina would be able to survive the old era.
Also it seems Seraphina will be able to transform too, albeit a less powerfull version of Seraphy since of what's said before and also the Key of Egg that deteriorates it seems. We have to note it's MTL of the article so it can be a lil bit wacky but it's still understandable.