Following the murder of her family, a girl named Aiko wakes up in a lab to discover that her own arm has been replaced by one from a hideous and powerful monsterand the arm has a will of its own! Agents from Aethosa mysterious, government-linked corporationwant to use the power of Aikos demon arm to fight the deadly creatures known as Chimeras, whose attacks on the civilian population are increasing. But Sudo, the agent who has befriended Aiko, isnt so happy about this development. In helping them to defeat this enemy, is she becoming an even greater threat herself?