The protagonist, Eito, suddenly finds himself gazing at the grand edifice of an otherworldly Library. Just moments before, he should have been in the confines of the academy's tiny library. The girl who introduces herself as the "Head Librarian" tells him this Library is a repository of every story known to existence. If the books in the Library are damaged, the stories they contain will be lost to the real world. "Well then, will you take up the position of Librarian?" Eito ventures into the world of stories as the Librarian who protects the Library. Many encounters with the characters featured in stories and the masterminds plotting disturbances behind the scenes await the newly minted Librarian Eito.