In an ancient kingdom, the sudden and mysterious death of the crown prince, who was to be the next king, triggers a series of events. Concurrently, the Library Tower, which holds every book in the land, is sealed off. Deep within the tower, where no one is permitted to enter, sits a solitary figure known as the Shishosei, the Chief Librarian. This being is a state secret: a human who possesses the supernatural ability to memorize and recite the contents of every book in the kingdom, serving as a living repository of knowledge for the king. However, the Shishosei is utterly helpless in all other aspects of life, unable to feed or care for themselves. A young barbarian girl named Kibi is chosen by divination to become the Shishosei's side woman, tasked with attending to his every need. As palace rumors and conspiracies swirl around the crown prince's death and the sealed library, the truth slowly emerges. The current Shishosei is actually Ren, the king's own brilliant son, who was selected by heaven for this fate. Unable to accept the reality, the king declared Ren dead and sealed the library. Kibi's presence begins to disrupt the rigid, secretive system, as she forms a bond with the Shishosei and inadvertently challenges the rules that govern him. The story unfolds as an intricate court drama, blending political intrigue, family tragedy, and the mystery of the Shishosei's powers. Subsequent arcs involve a crucial ceremony that threatens the kingdom's survival, the suspicions of the late crown prince's brother, and the expansion of conflicts to neighboring states, all while the forbidden relationship between Kibi and Ren deepens.