"Library War" is set in an alternate version of Japan where the government enacts the Media Betterment Act, allowing censorship of books and media deemed harmful. In response, the Library Defense Force (LDF) is established to protect intellectual freedom and oppose censorship. The story unfolds in 2019, focusing on Iku Kasahara, a determined young woman who joins the LDF after being inspired by a mysterious librarian who once defended her right to read a book as a teenager. Kasahara trains rigorously to become a member of the LDF’s elite Task Force, facing challenges both physical and emotional as she adapts to the demanding environment.

The narrative explores the ideological conflict between the LDF and the Media Betterment Committee (MBC), which seeks to confiscate and destroy materials it deems inappropriate. Kasahara’s journey intertwines with her colleagues, including her strict but caring instructor, Atsushi Dojo, who harbors a secret connection to her past. The series delves into themes of freedom, responsibility, and the power of knowledge, as the LDF battles to protect libraries and their collections from MBC raids.

Key characters include Iku Kasahara, whose idealism and determination drive much of the plot; Atsushi Dojo, a skilled and disciplined officer who becomes a mentor and romantic interest; Hikaru Tezuka, a calm and analytical team member; and Asako Shibasaki, a librarian who provides insight into the importance of preserving knowledge. The series balances action-packed sequences with moments of character development, highlighting the personal struggles and growth of its protagonists as they navigate their roles in the fight for intellectual freedom. The story also examines the ethical dilemmas surrounding censorship and the societal impact of controlling information, creating a thought-provoking narrative within a unique and engaging setting.