A case of insomnia swept across the globe. As a side effect of the drug developed to suppress this sickness of causes unknown, the "bloodivores" were born. Born from bloodivore and human parents, protagonist Mi Ryu was known as "The Child of Hope" tying bloodivore and humankind together. However, when Mi Ryu is arrested as the principal offender in a bank robbery, he is taken to a special prison operated by the Bureau of Special Threat Management for observing bloodivores.
The prison is then attacked by mysterious monsters that suddenly appear. Mi Ryu and Anji attempt to escape together but are confused when they discover the prison is located in the abandoned city of Aori. Why have the captured bloodivores been sent to Aori? Who or what are the monsters living there? Forced to fight against the monsters, the protagonist and his friends work to unravel these mysteries.