WARNING: This review contains some mild spoilers.I quite like this anime. The story -- an Ordinary High School boy finds out he's the key to a great battle between rival ninja clans -- isn't particularly original, but it becomes quickly obvious that the show isn't really about that. Rather, it's about the slowly evolving relationship between our main character, Miharu, and Yoite, another young man of an opposing ninja clan who is slowly dying -- and desperately wants something from Miharu.The relationship between these two kindred spirits is fascinating, as we begin to slowly understand how alike their struggles with happiness and apathy are. How healthy this relationship is, is always in doubt, and trying to come to terms with just how they feel about one another and how this affects both them and the people around them is one of the joys of watching this series.These two characters are trying to figure things out right along with the viewer, which leads to quite a bit of side-switching and motives and actions that aren't always readily clear. This is interesting at first, though it does get tiresome after a while; however, it dovetails nicely with the series' message that no one is truly good or bad, or trustworthy, and that you can't rely on others to make your decisions for you.This also reflects in the moral complexity of the various other characters on the show. Very few people in this series are all good or all bad; most of them are quite human, and as such are always surprising you. You come to really care about these people, because they seem so real; and even the ones who are at first unsympathetic or annoying slowly endear themselves to you (though I hated Kotarou right to the end).The series is at its strongest when it takes advantage of all of the complex characters. When the series, especially towards the end, focuses more exclusively on the relationship between Miharu and Yoite, it becomes bogged down in a repititious cycle of storylines we've already seen. Though the relationship between the two is fascinating, it isn't quite fascinating enough to sustain the entire series by itself, which is exactly what it tries to do for a while. Needles to say, this part is the weakest of the series.The strongest parts are a raid on a school towards the middle, and the ending, which manages to be completely awesome right up until an unfortunate deus ex machina that leaves the final few episodes to again mostly be about the relationship between Miharu and Yoite. Still, the ending packs a punch, and is certainly satisfying in the way it manages to tie several different plot threads together.It would be a shame if I didn't mention the remarkable animation -- the background is, I believe, gorgeous watercolors, and the character designs are dynamic (if a tad unoriginal). The characters are a little lanky, but still look great, especially when they spring into action.In short this is a very good series that at times sinks under the weight of its own fantastic characters -- if everyone around Miharu and Yoite wasn't so interesting, we wouldn't notice they're absence; of course, these are some great characters, which means that we do. By and large, however, this is a great and interesting series, well worth your time.