The killer's interview

Ha-Jun lived alone with his grandmother after losing his parents. After learning the truth about their deaths, he became a police officer, but life as a local police station officer is nothing but grueling, far different from the life as a detective he had dreamed of. *“I wish legendary detectives would appear before me and at least give me some clues about the cases.”* Frustrated, he visits the greenhouse where he lived with his parents as a child. There, he discovers one of his father’s books. When he opens the book, what appears before Ha-jun’s eyes are legendary serial killers? Wait, why the hell are YOU guys here?! (Source: KakaoPage, translated)