When "Cynthia," a young girl held captive in a mysterious laboratory, woke up, she felt something strange in her body. Her body was possessed by Belial, a vicious life form created by the institute. The taciturn and calm Cynthia, and the maniacal and depressing Belial. The two seem incompatible with each other, but both have a desire to get out of the institute. In the end, they use each other in their relationship to escape from the institute. When the girl ``Cynthia'' woke up, she felt something strange about her body. Her body is possessed by Belial, a vicious life form created by the research institute. Cynthia is quiet and calm, and Belial is ferocious and annoying. Although the two seemed to be at odds with each other, they both harbored a desire to leave the institute. In the end, they aim to escape from the research institute as they use each other.