Yoo Ji-cheol used to be a former undefeated boxing champion, beating all strong boxers of the world in his 20s. He fell in love with Sun-joo at first sight and proposed to her 3 days later. Together they have a beautiful daughter named Young-son. He was the national hero, beloved husband and respected father. However during the 19th defense match against Min-woo, he lost helplessly and was even suspected of match fixing. The whole world criticized him and he was permanently banned from boxing. He lost all his money, honor and family overnight. Ji-cheol then becomes a detective on the serious crime squad. He has absolutely no drive and always look for ways to slack off, He gets enthusiastic for a change during the illegal gambling regulation period and goes out with his partner to arrest gamblers. However he attacks a civilian who was taking a shower and is in danger of getting fired for sexual assault. To make matters worse, he was caught with money from a gambling house owner which he did not want to take and was suspended for 6 months. Having no money to pay rent and support his family, Ji-cheol made a dangerous decision to participate in an illegal boxing match for the prize money.Yoo Ji Cheol used to be a top boxer. After hitting rock bottom, he decides to gain control of his life again through mixed martial arts.