A womanizer and a cute woman (in a 10 year relationship going nowhere) on business trip are seated next to each other on a full train from Seoul to Busan. They start talking when she accepts she can't escape him.

On a television show billed as “the greatest fight show on Earth,” eager amateurs with lots to prove boldly step into the ring and expect to leave bloody but victorious. The ratings hungry producers seek out “legendary” but largely forgotten streetfighters and mine their desperation for recaptured glory and redemption into ratings gold.

A corrupted customs officer, Choi Ik-hyeon, faces losing his job. Then, his life turns around as he meets ganster Choi Hyeong-bae who has connection with the Yakuza. They quickly form a partnership; Hyeong-bae helps Ik-hyeon set up a business with the money from drug trafficking while Ik-hyeon lobbies for his partner Hyeong-bae. As the government declares war on crime, however, their partnership begins to crack.

Kyung-chul is a dangerous psychopath who kills for pleasure. He has committed infernal serial murders in diabolic ways that one cannot even imagine and his victims range from young women to even children. The police have chased him for a long time, but were unable to catch him. One day, Joo-yeon, daughter of a retired police chief becomes his prey and is found dead in a horrific state. Her fiance Soo-hyun, a top secret agent, decides to track down the murderer himself. He promises himself that he will do everything in his power to take bloody vengeance against the killer, even if it means that he must become a monster himself to get this monstrous and inhumane killer.

Tae-Sik is a widower with a mysterious past. When a young girl he befriends is kidnapped by a vicious drug gang, Tae-Sik rushes to save her.