The year is 2019, Japan has become like a war zone, the two major groups that fight each other are the militarized Betterment Special Agency, which regulates all kind of media and against them is a group called the Library Brigade.
The main character is named Kasawara Kaoru and her goal is to become a defense member of the Librarian Brigade, she undergoes strict training in secret as she does not want her parents to know about it. Kaoru has dreamed of becoming a member of the Brigade since she as a high school student was saved by one. Finally she gets accepted and joins the elite members of the Library Special Brigade.