Iku Kasahara wants more than anything to be an ally of justice--just like her prince. In the current age, the Media Betterment Act has allowed the Japanese government to impose heavy censorship on the expression of ideas, particularly those from books. When her favorite childhood book was marked for censorship, Iku felt that oppression firsthand, but she (and the book) was saved by a man from the Kanto Library Defense Force... her prince! Inspired by his example, Iku joined the Kanto library to safeguard expression of freedom, all while searching for the man she idolizes.