The premise looks like something out of the gender-bending manga/anime of the 90s, but the execution of it is rather ham-fisted.
In short a bunch of people turn into girls (with different personalities if they are already a girl) in order to fight and gain different powers as a result of the transformation.
The main character is caught up in this mess, but so far the manga has spent more time explaining the rule system than it has developing its characters, and has as a result floundered a bit.
This may be because they are trying too hard to fit in the exposition from the novels, but for whatever reason, I'm not liking the adaptation.
