The animation was a little strange, although I couldn't say it was bad. The problem was with the depiction of emotions on the characters faces, they all looked a little off. The same issue can extend to the characters themselves, though. It is difficult to empathize with any of them and the rushed nature of the script doesn't help.
The story is about young assassins, trained by people with no scruples. The violence scenes are really complicated, but also amateurish. They often end in the assassin almost failing and managing to survive by using some prop. Then you find yourself wondering why they didn't use that from the start. There are also a lot of sex scenes, bordering on rape, but they are kind of pointless after a while.
Bottom line: the atmosphere was great and the sense of desperation and dark foreboding was clearly why so many people liked this. However the story itself, while predictable and simple, was clearly meant to be more and the anime failed to capture it. The animation is simplistic as well. I watched the 2014 movie a week ago and, frankly, I think that the movie was better, moving the story in a different but good direction, while being clearly more carefully created.
