There is a man who delivers the most painful death to hardened criminals the law can’t judge: Hiroki Dan, Metropolitan Police Department Homicide Division. The son of the former commissioner, he seems to be on a solid career path. But in secret, he’s a serial killer who’s murdered over 100 criminals. An eye-for-eye murder suspense story begins in this spinoff of “Trace: Forensic Scientific Researcher’s Recollections.”