The manga is based on a novel of the same name that author and game creator Fummy released as a prequel to the creator’s own Majo no Ie (The Witch’s House) survival horror game.
The original free game launched for PC in October 2012 and Kadokawa published the novel with illustrations by Oguchi in October 2013.
The prequel novel centers on the story of how Ellen became a witch.
The game’s website links to an English translation for both the game and the novel.