An unassuming father becomes a target when he kills his daughter's abusive boyfriend — who happens to be the son of a cold-blooded crime boss.
Tsukasa, a college student, is rescued from an attack by a devil, one of many vampires that can blend in among the human population. Anzai, her savior, is a half-devil who exploits his supernatural gifts as a member of a shadowy police task force that specializes in devil-related crime in Tokyo. As Anzai continues to keep guard over Tsukasa, the two quickly forge a tentative bond—one that Anzai fears will test his iron-clad rule of never drinking human blood...
Ron Kamonohashi was once regarded as a genius at the top detective training academy. But after a fatal mistake, he was expelled and forbidden to become a detective. Years later, police officer Totomaru Isshiki knocks on Ron’s door seeking help on a serial murder case. He finds Ron, now a messy-haired recluse, who agrees. Together, this mismatched detective team begins solving their first mystery!
Two police detectives with different beliefs about the value of people's lives must cooperate to solve their city's most serious crimes.