The Detective Lady is Dead, I Did It

In a world where science does not apply, detective work is all about remembering three key elements: 1. The detective lady is impossible to be the perpetrator; 2. There can never be a perfect crime; 3. Cases involving supernatural powers require a detective with supernatural powers to solve. A hint is given that the murder weapon, now in the killer's hands, is a watermelon knife. Lee An gazes at the watermelon knife in his hand, pondering the implications, while looking at the lifeless detective lady.