Good idea in theory, the anime switches between slice of life with cute girls going to an all girls high school and bonding (one is a spunky and yelly girl, while the other is a cool and refined beauty) to drama about their past and an alien army invasion plot that ramps up in the last few episodes. I did enjoy the english dub with Hilary Haag and Monica Rial as the two main girls. The reason why this is hard to recommend... its specifically cause of the ending, it ends so abruptly and doesn't give too much closure, like they needed one more episodeor something, so I googled if there was an OVA or something and it turns out this is just a prequel to two manga that is set like 1000 years before those take place.

I think its cool that its original content though instead of just adapting the manga, may read it someday even though it wont really give me closure for the story this anime tells.