本作はロスト＝ストーリーは斯く綴れり（https://ncode.syosetu.com/n6161h/）の外伝作品です

Marte is a one-armed boy, the grandson of the former Pope of the Magic Nation De La Peña, born and raised in the First Holy Land, Malacanan. Although he had long been resigned to his own life, a major incident involving the wicked art of "Melting Magic" erupted in Malacanan, changing him. Through this turmoil, he met many individuals, including the Sage Auros=Elgarden, found a new purpose in life, and began to aspire to become an archaeologist specializing in dark arts.

Two years have passed since that incident subsided.

Marte visited the Fifth Holy Land, Anfield, and headed for a building rumored to be haunted.

It was a "castle," a structure that shouldn't exist within a Magic Nation.

And awaiting him in that castle were a mysterious silver-haired woman and strange magical entities that moved about of their own will――――