Dantalian no Shoka

Following World War I, England is the setting for this tale. Hugh Anthony Disward, also known as Huey, receives a mystery key following his grandfather's passing and, in accordance with the terms of his grandfather's will, is required to take custody of the Bibliotheca Mystica de Dantalian in order to inherit his estate and all of his assets. When he first meets Dalian, a little child residing on the estate, he finds out that she is in charge of the Archives, which are home to thousands of "Phantom Books" that contain prohibited knowledge. Huey helps her in looking into instances of people abusing the power of the Phantom Books, most of which result in tragic outcomes. He then uses his position as Dalian's new Keykeeper to lock the power of the Phantom Books and bring peace to the region.