This anime is great btw, but for those who have deep understanding of human emotions. Each and every character in this anime touch the different types of personality( not angel, gods n human and this is the concept btw, about which author gave no hints)how they live their life. The author explain the concept beautifully for those who can understand.
But when you write or create stuff like this you should made it for common peoples or everyone which he failed to do so. So this anime is not so good and good. It is for the selective audience.