Lord of the Dolmens

In a city storm drain, a girl chained to a concrete wall is found. She claims that the man who kidnapped her comes and reads a fairy tale about the Dancing City. And… brags that he shelters children. How do you get rid of a nightmare if you are the nightmare yourself? A mysterious voice on a smartphone offers an unusual therapy, where he must kidnap children and hide them underground. What are these terrifying experiments for, and what does the diary from his childhood hide?