During the coming-of-age ceremony for Oz (heir to the Vessalius family), “the messenger from the Abyss” suddenly appears and casts Oz into a prison called “the Abyss (in a different dimension)” for the crime of which he knows nothing about.
Wandering in the darkness of Abyss, Oz meets a mysterious girl named Alice who is also known as B-rabbit. Alice is one of the “Chains” in the Abyss and she is a black rabbit in Chain form. In order to leave the Abyss, she was waiting for Oz who will be her human contractor.
What is Oz’s crime? What is Alice’s intention? Their fate starts to unfold.