As the anime progressed, I found that the more episodes I watched, the more interested in it I became. Seeing as how there are three main story arcs in this short anime, I would say that they get better and better. The first story arc was a little dull for my own taste and the action only came in closer to the end. The second one got a little more interesting, and the third finally gave us that battle/war story line that had been hinted at during the previous episodes.
There are several reasons that this anime may be a turn off for some people, such as the very VERY strong and slightly uncomfortable relationship between the main siblings, the very quick escalation of sometimes rather grotesque violence, and the fact that there is little character development. However, the violence is in no way bad enough to be considered a horror/gore anime and let's be honest, many great anime do have that unusual sibling bond. As for the lack of character development in the main character, that is something which the audience just has to be fine with in order to fully appreciate this short anime for what it is.
One point of this anime I was satisfied with was the characters. Even though the number of important characters increased during the second story arc, each character had a unique personality to them (for the most part as far as the important characters go) that added to the story. Another aspect of this anime I enjoyed was the overall concept. The way that it was set in the future and used a combination of sci-fi/mecha with fantasy/magic was rather pleasing for me, seeing as how I have a hard time watching straight up mecha anime; they managed to combine the two in a successful way that made sense and didn't get too jumbled together.
The biggest downfall to this anime was the shortness of it. Unfortunately, shorter, more rushed anime are what is to be expected these days I find. When it ended, I found myself wishing that there had been more to it as I was still left with a number of unanswered questions. Watching the final arc, I found myself eager to get to the next episode, hoping for answers or further character development on some of the newly introduced characters, but found myself rather disappointed when the final episode came to a close and I had many questions still. The story to this anime had major potential had it gone further to touch on more aspects in further detail which makes me wonder about how much further the story went in the manga.
