Chikage grew up in the shadows of Shumisen, a clandestine organization that seals mononoke demons by binding them with mystical spirits called "In." His childhood fractured when his father was killed by traitors to Shumisen, and the trauma left him withdrawn. Years later, he acquires the power of "In" and receives an undercover assignment to execute the traitors within the society. His childhood friend Mahiru also gets pulled into the fighting that breaks out in their hometown of Takaamahara. The special is a single episode of action and science fiction.