Kampfer are girls with special abilities respective of their weapons (gun, blade, chained weapon or elemental summoning ability) who are chosen by a race of aliens called "Moderators" to fight to the death.
Natsuru Senou is an ordinary highschool guy who one day woke up as a girl as he was chosen to be a Kampfer (although he is a guy). When another Kampfer is present, or he needs to use his ability, he transforms into a girl.
In a Nutshell:
A sexy-cute yuri fan service if I ever seen one. There's a lot of girl-on-girl turn ons and harem ploy (but in this case, all of them are girls, with the main "girl" Natsuru as the harem master). A confusing, gender-bending love story for the un-initiated...but a light hearted treat for yuri fans.
Very nice character design and animation. A lot of inside jokes about "seiyuu" actors in the beginning of the series that might tend to alienate those not closely following seiyuu actors.
A lot of exagerrated circumstances that, thinking about getting into the same in the real world, would seem too much.
Only the main character's backstory are developed, leaving you to wonder what happened to the other supporting characters.
Story is crammed into the 12-episode series. I wish they developed that characters more, and their relationships with each other.
Weird dance moves by the main characters on the ending theme.