An isolated human colony ship is on the run from aliens and the only effective defence they have left are giant robots. No doubt, you've heard similar setups before; but Knights of Sidonia plays the situation completely straight -- from the real world physics to the societal implications.
Good -- A Society Built for Space
One of the most interesting points in Knights of Sidonia is the colony ship Sidonia itself and the society inside it. The Sidonia is basically built out of a fragment of the long since destroyed Earth. Thus, most things inside has a cobbled together look -- especially the buildings themselves. It is clear the humans who inhabit Sidonia had to adapt to their extreme circumstances as best they could.
Of course, this goes far beyond the setting itself. After years of war against the alien forces of the Gauna, the humans had suffered such losses that normal life looked to be impossible. To combat this, they adapted through genetic engineering. The humans of Sidonia rarely need to eat. Instead they draw most of the energy for daily life through photosynthesis. Thus, when Nagate, our main character who is genetically still like us, enters the story, he is a clear outsider -- for from their perspective, he eats and poops all the time.
Moreover, we see that Sidona also has a hermaphroditic third gender which can act as either male or female -- whichever is most needed to bolster the population of Sidonia. It is always interesting to see how this third gender is treated. Sometimes they are seen as "one of the boys" while at the same time look to be possible romantic interests. Exploring the society of Sidonia never ceases to be captivating.
Good -- Real World Physics
Many science fiction tales -- especially space operas -- play it fast and loose with physics for the sake of a good story. Knights of Sidonia, on the other hand, embraces real world physics and uses them to build a compelling story.
The Sidonia is really just a normal city built inside a giant rock. Thus, even something as simple as turning the ship can have catastrophic consequences for those living inside. G-forces increase, buildings strain and collapse, and people fly into walls and splatter if they are not tied down in some way. It is a terrible sight but explores the consequences of realistic space travel in this situation.
The mecha also follow real world physics and so g-forces, power, and oxygen are all constant concerns in the story. Even inertia is a constant fear as once you get too far away from Sidonia, your inertia mixed with your remaining fuel can make it so that you'll never be able to return.
All in all, Knights of Sidonia makes you really think about how much we take for granted in other sci-fi stories.
Mixed -- Playing it Straight
When it comes down to it, Knights of Sidonia is a clear deconstruction of space operas like Macross and Gundam. It takes a look at the tropes associated with this genre and plays them all straight -- as if it were the real world with the same physical laws. Thus, as mentioned above, the mecha pilots have to worry about fuel, and problems like food and water for the population of Sidonia are constant obstacles to be addressed.
Beyond that, something as simple as "young boy becomes Gundam pilot" is torn apart as the other characters react naturally to the absurdity of this idea. Some take it as a joke, while others react with jealousy.
It also is very keen to show what would really happen when you send half-trained kids out to fight something as otherworldly as the Gauna -- i.e., a lot of pilots are going to die. Watching how Nagate and the rest of the cast react to the deconstruction of these tropes is half the fun of the series.
However, there is also a downside to building your entire show set firmly in the real world: It becomes harder and harder to suspend disbelief when something nonsensical comes up.
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The biggest example of this is when Norino, Nagate's squad commander, becomes jealous of Nagate's skills and prestige and thus decides to publicly shame him -- and possibly even kill him. Norino's plan to do this involves giving Nagate the order, over a private frequency, to detonate a bomb early. Thus, it will look like Nagate jumped the gun and caused the whole mission to be a wash. His plan, for the most part, succeeds -- though it has an unexpected death toll.
Of course, all I could think as the post mission drama played out was, "Do you mean in a world this realistic, Mecha don't have flight recorders?" It is an oversight so in contrast with the realistic world of Sidonia that it feels like the only reason the mecha don't have flight recorders was just so this drama could happen -- and that is just badly contrived writing.
Bad -- A Bit Heavy Handed
Knights of Sidonia can be too heavy handed in its storytelling -- especially when it comes to trying to build emotional moments. Characters are introduced, given an episode of development and then killed off for a cheap emotional reaction. This is so obviously done that by just a few episodes in, the moment characters get a backstory they might as well be waving a giant flag while screaming that they are about to die. The first time a character we get to know dies, it's shocking -- further setting up the realism the story is trying to create. But from that point on, it's just a trick that is reused far too often to have any great impact.
But the oddest single ham-fisted bit of storytelling is when a character is given a character development scene after her death via flashback -- like the show is saying, "Oh, she died and this is why you should feel bad." It was not the least bit effective emotionally and fell completely flat.
All in all, Knights of Sidonia is a great deconstruction of the space opera genre. The world it presents is well thought out and built to explore the implications of an isolated human colony ship fleeing through the stars. The inclusion of real world physics and worrying about things like food and fuel makes the series feel a lot like Battlestar Galactica (2004). So if you want a realistic twist on shows like Macross and Gundam or are just looking for an engaging science fiction anime, you should definitely give Knights of Sidonia a watch.
Knights of Sidonia aired on TBS in Japan. A second season will be airing in late 2014.