Angel's 3Piece!: Kurumi Nukui

Kurumi Nukui is Kyō's little sister who usually berates him for his decision to not go to school, but loves to be by his side. She is also a classmate of Jun and the others and is a little jealous of them getting along with her brother.

Library wars: Iku Kasahara

Iku Kasahara is the main character of the series. She is twenty-two-years-old and is initially ranked Librarian First Class, but is later promoted to Chief Librarian. She joined the Library Defense Force's Kantō Library Base in 2019 after being inspired by a high ranking Kantō Library Defense Force member who saved a book she wanted to buy that was targeted for censorship. She holds this unknown person in high regard, thinking of him as her "prince", and she wants to be an "ally of justice" as he was for her. As such, she has a strong sense of justice when it comes to freedom of expression and is willing to put her life on the line for the books she has sworn to protect. When she enters into recruit training, however, she finds it to be very challenging, made especially so by her drill instructor Atsushi Dojo who pushes her harder than most other recruits. In high school, she had been a member of the track and field team, so she has a lot of stamina and drive to continue with the Library Defense Force.

Library wars: Asako Shibasaki

Asako Shibasaki is in the Library Task Force and is initially ranked Librarian First Class, but is later promoted to Chief Librarian. She works on the inside as an informant in military intelligence, and is very good at gathering information. She is Kasahara's roommate, and after Kasahara joins the task force, Shibasaki helps her study the catalogs in the base's library through a form of negative reinforcement involving giving her candy when she gave the wrong answers which leads her to break out in pimples.

Shibasaki is really sharp and brilliant; she's aware of facts most people aren't aware of.