It's an anime based on a Japanese social network game. (What's a social network game? Let me google... oh, okay. It's what you'd think, really.)
It's the year 2045 and aliens are attacking the Earth. Can your schoolgirls fight off the Irous? You have nineteen magical girls in the Hoshimori class of Shinjugamine Girls Academy... although that's "magical" mostly just as a genre label. The show looks like SF to me and I couldn't see any magic beyond at most the girls' transformation sequences. Meanwhile their outfits are more like armour and they fight with guns, swords, etc.
It's a bit of a mish-mash of an anime, to be honest. Sometimes it's about fighting aliens. The last few episodes grow a surprising serious plot. More often, though, it's slice-of-life school nonsense with an underwhelming cast. There are too many of them. That's a consequence of the original game design, but even so nineteen is too many. It took me ages to realise that Miki was the main character and even she doesn't have a huge amount of personality, although she's likeable enough. Of the others, the only ones I can remember are Misaki (mysterious warrior girl who came out of nowhere and disapproves of frivolity), Renge (pantomime lesbian), Urara (determined to be an idol), Anko (stay-at-home gamer with stupid hair clips) and... well maybe Miki's little sister. I'm being generous when I say I "remember" Anko though. That's mostly because of her hair clips.
There's only one male character and he's technically the Player. In the game, you play him. In this anime, though, he's been moved so far out of focus that you barely notice that he's there.
The school-based material is okay, although it would have been stronger with more focus. It's fine. It's normal schoolgirl anime fare. It's also forgettable, being watchable space-filler rather than anything you'd actually call good. I enjoyed it, but I'd struggle to tell you what happened in most of it. Ep.5 is about the relationship of Nozomi and Yuri, for instance, which is fine as far as it goes and perhaps even one of the better school-based storylines, but after that those two characters return to being background. Ep.6 is a body swap episode involving Kurumi (likes flowers) and Renge (...oh dear). Furthermore Kurumi lets Renge talk her into not telling any of the teachers, which means she's: (a) letting the sex offender stalk everyone in her body, (b) keeping quiet about the alien body-swapping power of a new, unknown species of Irous. That's criminally stupid.
My favourite school-based filler storyline might be the school culture festival in ep.9 and even that's a bit silly, really. It's amusing eventually, though, and manages to find quite a nice way of combining the show's two halves (aliens vs. school).
The Irous battle scenes are also okay. Girls fight aliens. It's a perfectly good example of that. Most of the aliens aren't too hard for the girls to defeat, but a Godzilla clone pops up halfway through and nearly nukes everyone, then later we get sinister enemies in cloaks. There's also a supervillain who lurks in the shadows and appears to be directing everything, but the show never does anything with her. Maybe they're holding her in reserve for Season 2? That's conceivable, but I'm not convinced that we'll get that second season.
The storyline's surprisingly serious, though. It's a slow-burner almost until the end, basically being about Misaki. She's surrounded by airheads and she knows that they're underestimating the Irous. She also thinks they're lazy and weak, since she herself is a hardened warrior with more combat experience than all the others put together. In ep.5, Misaki kills a monster with a groin blow. Imagine that for a moment. The other girls try to make her unbend and, over time, even succeed to some extent... and then the last two episodes spring some surprises on us.
This show's okay. It's neither good nor bad. I'd be surprised if they made that sequel and it's not strong enough for a recommendation, but I watched it happily enough. It's two or three passable (if generic) anime shows that have been scrunched together. Its designs are similar to Magical Girl Lyrical Nanoha, but I don't hold that against it. Eyes might roll at the odd scene or two if you watch it in company, but it won't make you want to curl up and die or anything. There's nothing actually wrong with it, although it would clearly be improved by having a smaller cast. It's acceptable.