Resembling a shattered toy chest, the mystical Abyss is a dreadful domain inhabited by monstrous entities known as Chains. The majority consider it merely a fairy tale, employed to frighten misbehaving children. Oz Vessalius, the jovial and prankish heir to the noble Vessalius family, is among those who hold this view—until, during his coming-of-age ceremony, the enigmatic Baskerville Clan arrives and sentences him to the Abyss for a transgression he did not commit and knows nothing about. Oz subsequently enters into a contract with Alice, a singular Chain capable of assuming human form, in an effort to flee the Abyss. While Oz strives to decipher the secrets surrounding his sin, the Abyss, and a calamity from a century prior, he and his allies face opposition from the Baskervilles and specters of the past. Concurrently, his quest to return home is beset by unyielding despair.