In a mysterious realm known as the Obsidian Theater, an amnesiac protagonist, known as The Devil, is trapped in a never-ending cycle of battles. Her sole purpose is to protect the Loom of Fate and the Ideal White, a powerful magic capable of granting wishes. Yet why she did that, she no longer remembered.

However, by the twist of fate, The Devil met a dying Hero, Milli. Instead fighting her, Milli offers her heart, the Magicore, giving the Devil a second chance to realize her desire. In return, she asks the Devil to remember everything and, when the time comes, to stop her from destroying the world.

Before The Devil can fully comprehend the situation, Milli vanishes, leaving a confusing message by calling the Devil her Mom. Determined to uncover the truth and understand her connection to Milli, The Devil returns to the world. This time not to hunt The Hero, but to save Milli.