Core setting: The male protagonist is a retired criminal police officer + private detective. He resigned due to the mysterious disappearance of his sister three years ago and was framed during the investigation. He opened a late-night detective agency, which specializes in taking on cases that the police did not answer, old unsolved cases, and man-made murders with supernatural appearances; the female protagonist is a forensic doctor and trace appraiser, with a cold and vicious tongue. But he has strong empathy and is the hero's only trusted partner; the second hero is a former criminal police teammate, upright but restricted by the system, and secretly delivers clues to the hero; the villain is the man behind the scenes (codename: Puppet Master) throughout the story, controlling the murderers of all small cases, and is directly related to the disappearance of the hero's sister.
