It may seem boring and tempting to drop in the first few episodes but the story gradually unfolds with new interesting plots and links. Art style is unique, similar to dororo and its a story without modern conveniences. It was predictable to a certain extent. Characters are mysterious and there was not a lot of background story other the anime reminding that humans toyed with fire and got burnt badly. Ending was a cliffhanger that stated will be continued in season 2. Quite a lot is shown without much details hence the score. Definitely a must watch if one doesn't mind the slow and boring start.