Dantalian no Shoka  

The Mystic Archives of Dantalian, Bibliotheca Mystica de Dantalian, Dantalian's Bookshelf, ダンタリアンの書架

Six months ago, a young man named Lord Hugh Anthony Disward, also known as Huey, lost his grandfather, Sir Wesley Disward. In order to inherit his family's manor and its contents, Huey must take care of the Bibliotheca Mystica de Dantalian-an archive that holds forbidden knowledge-and a mysterious girl named Dalian. As Huey settles into the manor, an old rival of Sir Wesley arranges a meeting with him. During this meeting, Dalian tags along and discovers that the murderer is in possession of a Phantom Book-a cursed tome that Sir Wesley tried to seal away. When the book puts Huey and Dalian in danger, they learn that the Bibliotheca Mystica de Dantalian and Dalian are one and the same, and she entrusts him with the key to unlocking the knowledge stored within her. Together, they seal the book away and form an unlikely partnership as they solve mysteries caused by other Phantom Books.