[Adults Only]Two ex-detectives who have fallen from grace in the city become patrol officers in a quiet town with a history of a notorious cold case: a serial killer whose signature move is laying cutting off the fingertips of the women he murders. The only suspect that the case ever had is one of the patrol officers, and his partner is here to figure out if he's a monster who's responsible for the murders, or a man who became a monster to find out who did it....

Choi Joonwoo is an 18-year-old boy who is used to being a loner. He is not good at expressing his emotions and doesn't try to establish rapport with others. But he has a cute and silly charm, and his life starts to change when he transfers to another school. Yoo Soobin is a top student as a result of her mother's ambition and extreme pressure. Without a clear dream and goal, she lives in a daze. Her real dream is to live independently. After she meets Joonwoo, her life gradually begins to change. Ma Hwiyoung is very handsome and gentlemanly, and everyone trusts him. But under his perfect appearance, he has an inferiority complex. He seems very tough, but he is actually very cowardly. When the transferee Choi Joonwoo appears, the iron wall he built slowly begins to crumble....