Aliens have targeted Japan, but they've done their homework. They know that the cuter the invaders are, the more likely human public opinion will rise against the defenders if they "bully" the invaders. What's needed are even cuter defenders ... Thus are Mao, Misora, and Sylvia - three cute eight-year-old girls - drafted to defend Japan from the cute aliens.
On the surface, this is yet another entry in the magical girl genre so popular in anime, and youngsters will happily take the show at that level. Look deeper, though, and you'll see a parody of the genre and a satirical look at military inter-service rivalry, along with a comment on creator Ken Akamatsu's inability to come up with different character designs (in the crossover episode with Love Hina). And the climax of the final episode is one of the finest Heartwarming Moments in all of anime.