The reviews on here tend to lead towards the negative side, everyone has a different taste so my recommendation would be to give this anime a go. Many people have criticised this anime carrying similar elements from Attack on titan however this was the one reason I was motivated to watch it since I was trying to find a similar themed anime.
When I first watched this, after 6 episodes in, I didn't want to continue on.
The plot was somewhat repetitive; my annoyance was growing but that is probably since I have no patience. None the less, I finished it and I am so glad that I did.
The plot suddenly bloomed and there were more questions arising inside me now. This was just the kind of feeling I needed: curiosity. Suddenly the anime itself seemed unique with the vampire, demons vibe more prominent and less of the humanity on brink of extinction.
Try it, I dare you. If you are a girl you might just fall in love with all the characters but that doesn't stop the vampire loving fanboys too! It breaks from conventional topics after a while and complete itself in a unique identifiable way.