Ji-cheol is an incompetent husband and dad. He was a detective who got suspended for allegedly taking a bribe. He can’t come up with their living expenses, let alone the rent. On top of that, his daughter gets into trouble and he has to come up with the settlement money. Cornered, Ji-cheol makes a dangerous decision. Having been a boxing champion in the past, he decides to participate in an illegal boxing match and take the prize money.
Jang Hyuk as Yoo Ji-cheol, Fallen father and fighter (43 years old)
Ji-cheol used to be an undefeated boxing champion in his 20s. He fell in love with Sun-joo at first sight, proposed to her in 3 days, and together they had a beautiful daughter named Young-sun. He was a national hero, beloved husband and respected father. However, during the 13th defense match against Min-woo, which was called the game of the century, he lost helplessly, which seemed weird, and the whole world criticized him. He lost money, reputation and the happiness of his family all at once. 11 years later, he suddenly gets an opportunity to make a comeback.
Son Yeo-eun as Choi Sun-joo, Ji-cheol's wife, an erotic novelist and massage chair salesperson (37 years old)
She met Ji-cheol, a top sports star, when she just graduated high school. Ji-cheol proposes to her, leaving Min-woo, who has had a crush on her for 3 years without even the chance. She marries Ji-cheol and has a daughter named Young-sun. Life with a national hero is luxurious. However, 11 years later, her national hero husband has been long gone and she is only left with a hopeless man by her side.
Young-sun had a happy life as a rising ballerina. However, the year Young-sun turned 6, her dad’s reputation plummeted for match fixing and everything changed. 17-year-old Young-sun doesn't study, dance and isn’t enthusiastic about anything. However, there is one thing she is secretly passionate about. She uploads videos on Youtube that are very popular. Although she quit ballet, she couldn’t do anything about her love for dancing. She posts videos under the identity “Cat Mask”.
Ha Jun as Lee Min-woo, MMA champion, sports superstar (37 years old)
He is currently number one in MMA middleweight rankings and very popular for his fighting skills. He is enjoying the golden age of his life. However, his family was poor as he was growing up, he was weak and had many scars. Sun-joo is the girl next door that was always by his side and helped him dream of becoming a boxer. He had a crush on her, but didn’t even dream of telling her and ended up letting her marry Ji-cheol, the top sport superstar during that time.
Kim Jae-kyung as Cha Ji-woo, Daughter of Dr. Cha, Ji-cheol’s former partner, a regional investigation unit detective (32 years old)
She joined the team much later than Ji-cheol, but became the youngest female lieutenant and Ji-cheol’s superior through several special promotions. Although everyone else looks down on Ji-cheol, Ji-woo likes him and is on his side. Not even she understands why, but she favors Ji-cheol. After Ji-cheol quits his job as a cop in shame, Ji-woo stumbles upon a mysterious case.
^ abIn order to circumvent Korean laws that prevent commercial breaks in the middle of an episode, what would previously have been aired as single 70 minute episodes are now being repackaged as two 35 minute episodes, with two episodes being shown each night with a commercial break between the two.