Tae-ju, a murderer serving a life sentence in prison, is given a temporary release to save the life of a seriously ill young girl, Se-hee, who suffers from Wilson's disease and desperately needs a liver transplant. Se-hee is the daughter of Yeong-woo, and old friend of Tae-ju's who is now a police officer. Upon discovering that Se-hee's now deceased mother was his ex-girlfriend, Tae-ju realises that he is in fact her biological father, and does everything he can to try and save her life.

Idol singer Eun-chae, on the verge of being expelled from the industry due to a scandal, suddenly receives news of her father's death — along with an inheritance: a heavily indebted taekwondo gym. Hee-chan, a former athlete who quit after an injury, is now an instructor at the gym. Together with his hobby-class students — each carrying their own story — he dedicates himself to training with the goal of winning a national championship. When Eun-chae returns to her hometown intending to sell the gym, her ex-boyfriend, Soo-yeol, a second-generation chaebol, makes her an irresistibly dangerous offer... Can Eun-chae, Hee-chan, and the hobby-class students overcome the endless hardships of reality and write a brand-new chapter in their lives?