First, there are many good things about this series. At the top is the story, which is one of the more interesting ones you will find in anime. There are many clever devices and inventions which provide additional interest. Next, there are many battle scenes which offer up action and drama, along with the essential problem of Sidonia - a huge space ship on which live people that have survived Earth's destruction by the guana creatures hundreds of years ago - which is survival against space itself, their aloneness in the universe, and the attacking guana. On the down side are some really stupid and impossible things that are strewn about in an otherwise great adventure. Primarily, there are the guana; they are simply impossible creatures that just couldn't exist any way at all in any universe or reality, ever! They are, apparently, stupid things, essentially blobs of who knows what, unable to communicate, they can manage sophisticated propulsion and space travel by no scientific means whatsoever, as well as utilize complex weaponry to kill their enemy (Sidonia), which is their enemy for no known reason. They can also occasionally transform into something that looks human-like, especially after they've eaten a human! Making relatively tiny Sidonia their enemy in an enormous universe where they could go anywhere (since they travel easily in space by who knows what means), is just dumb! Additionally, there is nothing that the guana creatures - or the Sidonians for that matter - do that is actually possible, which is where the series deserts sci-fi and becomes pure fantasy. This is okay, if the series is going to be pure fantasy, but it treats the storyline as sci-fi, which it isn't. Asking where does all the fuel to power everything come from, offers no answer - it's just there: magic! Which is not supposed to be what this series is about; and yet they employ it liberally because there is no even REMOTELY scientific way any of these things could happen.
Moving on, the characters are mostly decently portrayed, although, yes, you could develop them a little more, but that is not a major complaint for me, since the drama is not driven by the psychology of the characters; rather, it is the action that does it. The animation is okay, although not startlingly good (like a Disney or Pixar offering), and could use more coloration, instead of the drab grayish-bluish hue they cast over everything. Yes, I know everything's in space, but still, you can have color in space, and they do have a few scenes where they employ it.
Like most of these Japanese anime, having characters which are paralyzingly shy about their feelings for one another, or seeing each other partially nude, gets old; it's silly and unrealistic. No reason for it.
Tanikaze, our main main protagonist, is a strong pilot and soldier who shows the same spirit and bravery that our fighter pilots show today. He is charming in his own way because he is not an average alpha type male, but always maintains his shy & humble demeanor throughout, regardless of what he accomplishes; understandably, the women are attracted to that, along with his heroics. There are a few women he is close to, and that provides further story development.
Overall, despite the impossible "science," propelling things around by employing magic power and unlimited fuel, the story is a good one, and does pull you into its matrix. There are fairly attractive characters, good animation, and plenty of battle scenes utilizing mecha for those folks who love that sort of thing. Too many mysteries work against the storyline - what the guana are, where are they from, why kill people they don't even know and have never interacted with - but they don't completely destroy it, and so despite some of the scientific irritations, it's a worthy story to follow and a pleasant anime to watch.
