The Mystic Archives of Dantalian (ダンタリアンの書架 Dantarian no Shoka?, alternate title Bibliotheca Mystica de Dantalian) is a Japanese light novel series written by Gakuto Mikumo and illustrated by G-Yuusuke. The series started serialization in Kadokawa Shoten's light novel magazine The Sneaker on February 29, 2008. A manga adaptation by Chako Abeno started serialization in Kadokawa Shoten's shōnen manga magazine Shōnen Ace on March 26, 2010. Another manga adaptation by Monaco Sena started serialization in Kadokawa Shoten's seinen manga magazine Comp Ace on March 26, 2010. An anime adaptation began airing on July 16, 2011.

Plot:
After the death of his grandfather, Hugh Anthony Disward, also known as Huey, receives a mysterious key and according to his will, must take custody of the Bibliotheca Mystica de Dantalian in order to inherit his estate and all his possessions. Upon meeting Dalian, a child living at the estate, he learns that she is the guardian of the Archives which contain forbidden knowledge stored in thousands of magic books called "Phantom Books" (幻書 gensho?). Upon agreeing to become Dalian's new Keykeeper, Huey joins her into investigating incidents regarding people misusing the power of the Phantom Books, most of them with tragic consequences, and using his power as Keykeeper to seal the power of the Phantom Books and restore order to the area. (Via Wiki)