It assumes you have watched at least the first volume of the original show, and even if you haven't that's still okay imo. Most of the people negativity reviewing this only watched the first 3 episodes, and dropped it after that or didn't change their reviews. Claming it was doing a disservice or disjustice to the original, and generally just coming across as snobby. I get the impression they assumed this was going to be a remake, which it is not, and were dissatisfied with the "rushed introduction" in the first 3 episodes. (A side note which bothers me, the same people say they rushed through the first volume like it was nothing. And while it was sped up a bit for the sake of lack of redundancy, those episodes are only 4-7 Minutes in length including the intro and an albiet short ed. So if you see those types of criticisms, keep this in mind.) With that all out of the way, this is more of a side story focused on character building (specifically Weiss, and mildly Blake). Something which, while I thought dragged on at some moments, was done very well. If you're coming into this from a binging perspective this might be alleviated some. The story will diverge around episode 4 to 5ish. The animation is great through and through, I legitimately cannot understand how people are criticizing it. It's one of the best looking shows this season, and visually leagues above the original. The choreography is nice too, on par at times (but maybe not better than) with the original though. They were moments of CG here and there, and while I could criticize that, I honestly just thought of it as a laughabley enjoyable homage to the original.
I'm dragging on here, I inteded for this to be quicker than it ended up being.
Tldr: Don't let the people who only watched the first three episodes and negatively criticed this deter you from watching it. ITS NOT A REMAKE. If you're a new or old fan, you're sure to enjoy this. Here's to hoping for a season 2 of sorts (how ever that would play out)!
