Zero is a student from Cassell College who hides a mysterious past.

Spoiler

Sold to Herzog by her parents at a young age, she was taken to the Black Swan Bay facility for experimentation purposes. One night, after she nearly fell into despair, a ghost-like black snake came to her rescue. Deciding to investigate the creature, she sneaked out of her room at night and discovered a boy in the forbidden Room Zero. The boy told her to call him "Zero" (shortened to Z) since he didn't have a name. The pair vowed to remain together forever.