They seem to be using the plot points from Bloodlines and Aria for this initial season of Nocturne, it appears. Which I guess is okay, except it would make any plans for either of those stories (more probable is Aria, honestly) kinda shot.
I'm less impressed that they are taking sincere liberties with the maidens from Rondo, turning both Annette and Tera into magic users suddenly as if having Maria wasn't enough. Granted, I'm all for straying away from the "damsel in distress" trope, but it seems forced here.
However that pales in comparison to them showing us Richter's mother as this badass whip-wielding female Belmont, FINALLY after we've all been wanting another shot for one, only to kill her off for the sake of injecting trauma into yet another character's story where it wasn't needed. It feels like she's just this disposable character they made up with the purpose of fridging to make poor Richter angsty....because we all loved that when that was done in S3 of the OG series.

Anyway, those are my thoughts. Animation looks solid and I'll allow some of those liberties slide if this is meant to be a prequel to Rondo's story in season 2 and the story ends up being better than I'm fearing.