Oz Vessalius, the 15-year-old heir to the prestigious Vessalius Dukedom, lives a life of leisure—until his coming-of-age ceremony turns into a nightmare. A group of mysterious figures known as the Baskervilles arrive and condemn him to "The Abyss," a terrifying parallel dimension, for the "sin of his existence." Inside the Abyss, Oz encounters Alice, a powerful "Chain" known as the Bloody Black Rabbit, who offers him a contract to escape. Returning to the human world, Oz discovers that ten years have passed. Joining the secret organization "Pandora," Oz and Alice embark on a quest to recover Alice's lost memories and uncover the truth behind the Tragedy of Sablier—a century-old catastrophe that holds the key to Oz's past and the dark destiny that awaits him.