Just... it had the audacity to have promise and failed to fulfill it at literally every juncture. Rushed development of characters and strange, nonsensical personality shifts. Terrible plot that was both predictable and disappointing.
Vampires were awesome. Fine was pretty awesome if an overly dramatic joykill, and we never even got to see her kick butt.
Momo was alright if a bit passive and overly naive/optimistic at silly times in true anime protagonist fashion.
Villains were comic book level ridiculous at almost every opportunity which made it impossible to take seriously.
Romance was a bit on the subtle side with them for me, they were awfully coy about addressing the fact that they were in love with each other, which I didn't see the point of. And of course the culmination of the story utterly failed to satisfy.
It was just so predictably bad in that it fell into all the classic but terrible trope traps, which would have made it a 2 star or so, but honestly the potential it showed made it worse, because I actually had hope for it multiple times, and then was let down.
I'm not mad, just disappointed.