Mermaid! Damian and the officer! Dick's story.
Dick Grayson is a police officer with the Gotham Police Department. Because one day she cared for a lost boy on the street, and then stepped into an underground world that she had never known before. Due to the disappearance of the Dark King in Gotham's underground, various monsters continued to appear and commit various crimes. Damian and Dick, who aspired to become a new generation of emperors, began a secret mission to capture and subdue the monsters. As the underground world deepens, the dusty cases of the past begin to unravel, and the relationship between Damian and Dick also moves towards an unknown future... Can they solve these?