Lets say this: the first 12 episodes are quite sloppy as far of animation goes, the rhythm can be really slow and hard to swallow but if you have the guts to pass the first 12 chapters (which is a lot I know!) then the story regains fly and begins to develops a little better, the animation improves enough to enjoy the story. By the time you reach the last chapter you end up deep in sadness and despair because you commit yourself to those characters and their story, you feel empathy for all of them and their tragedies and wish they somehow reach ahappy ending which will never come and then, realize this is truly a masterpiece. The big turn down however, are the first 12 chapters which lets be honest, an average anime viewer can drop it at the very first episodes. So yeah, it can be hard to follow. I recommend reading the manga instead if you drop the anime but don't miss this story!