"Until the demon lurking among the participants is slain, this game shall not end." Lady Hermina, the daughter of the Count Einhorn, finds herself entangled in a deadly game called the "Summoning Ritual of a Wicked God" within an ancient northern castle, alongside her childhood friend and maid, Charlotte. Among the eight participants at the castle, two are designated as "demons," tasked with murdering one person each night. Those who are not demons must execute a suspicious individual through daily voting, participants are unable to leave the castle until all demons are annihilated. In this game where death looms, Hermina must use all of her wits to survive, while trying to protect Charlotte, but...!? (Source: Lanove, translated)