Kuze Tsugumi, daughter of aristocrats, agrees to be married to save her family from decline. But before she goes through with it, her younger brother Hitaki gets her involved in an incident caused by a "maremono," a type of book that casts a great influence on whoever reads it.
As a result, Tsugumi gains the power to see "aura," a light that represents the emotions that dwell within a maremono. While still reeling from everything that's happened to her, Tsugumi is confronted by a person from the Imperial Bureau of Library Information Resource Management, also known as "Owl," an organization that preserves and manages maremono, and requests her aid in investigating them.
Despite her reservations, Tsugumi decides to join the maremono investigations at Owl, but...
This is the story of a woman whose destiny seems to sway up and down, as if on the delicate balance of a scale.