In 1989, the Japanese government enacted the Media Betterment Act, which empowered a group of soldiers called the Media Betterment Committee (MBC) to destroy and censor any "problematic" media under the pretext of safeguarding public morals. In response, regional governments formed the Library Defense Force (LDF), whose members take up arms and risk their lives to defend freedom of expression. Leading the Kanto branch of the LDF is the Library Task Force (LTF): an elite squad composed solely of the most exceptional fighters. As a high school student, Iku Kasahara witnessed the terror of censorship firsthand when she refused to hand over the latest volume of her favorite series to MBC agents. She emerged unharmed only because a lone LDF member protected her and her cherished book. Now in her 20s and still unable to forget the man who saved her, Kasahara joins the LDF, hoping to become just like her prince. However, LDF training proves far more grueling than she could have imagined, and her instructor, LTF member Atsushi Doujou, seems determined to make her life a living hell. Given her struggles, Kasahara is shocked when she is selected as one of the two new LTF recruits based on Doujou's recommendation. As Kasahara does everything she can to prove herself worthy of the LTF and uncover her enigmatic superior's motivations, she wages war—both on the battlefield and in her personal life.