This is one of the best anime I've ever seen (and continue to watch since its second season is still airing) in my life. An anime that surprises by proving to be the complete opposite of what it appears to be at first, with a incredible story and very, very well developed characters. Not to mention the excellent animation work it has from one of the best studios today. The soundtrack is the best, especially the last opening which is too catchy and hard to forget.
Excellent recommendation.