Sky Girls starts off as a simple enough fanservice-fest: girls dressed in swimsuit-like "nanosuits" in exoskeleton-like mecha! They're the 'ultimate weapon' against the cyber-enemies 'WORM' -- battle machines that have wiped one third of humanity. The 'Sonic Diver' mecha have been created to fight against a re-emergence of the WORM, and since males are in short supply because of the casualties in the previous war with the WORM, girls are recruited to pilot the mecha. Of course, there are many 'old hands' in the military who think it's a total disgrace to have teenaged girls do battle -- but at the moment the series starts, there is no alternative.
Main character is Otoha, who gets drafted into the Sonic Diver team. She is an expert in kendo (her family runs a dojo), but she's not especially skilled in anything else -- she is selected because her physique allows her to sync up with the nanoskin armor that protects the pilot. Together with the three other girls (with two more added in as the story progresses), she is stationed in Oppama base, forming the Sky Girls team.
It all starts off pretty innocent: the setting is pretty 'military light', with plenty of opportunities to get into trouble without any real consequences. There's sleuthing about who wears these enormous bras, the obligatory onsen episode, etcetera. But there's some serious stuff going on as well, with the team training a lot and learning what it means to work together.
It turns out that the WORM are actually a mutated form of nanobot, that was created by Dr. Krishnam to cure his daughter Aisha from a disease. However, the WORM now seem to think they should protect the Earth's ecosystem and have since been targetting polluting installations like coal power plants etcetera. Later on in the series, Aisha makes an appearance and shows limited remote control of the WORM.
The whole base is packed up and placed on a ship that sets sail to the WORM hive to destroy it once and for all. Of course, everything that the WORM have absorbed in the past gets thrown at the crew, and of course Otoha's twin brother who dissapeared long ago also makes an appearance. Through some intense fighting scenes, everything ends up OK again..
There's not much in this series that is extraordinary. Designs are kinda bland, animation is kinda bland, plot is meh. The usual themes like friendship, working as a team towards a common goal etcetera figure heavily in the series, but not in ways that are particularly novel. But there's not much to distinguish this series from many, many others.
- Some episodes are amusing takes on common themes like "stranded on a jungle island";
- Enough fanservice.
- Bland all the way.
All in all, this series doesn't rise above a mediocre 6.