As a caring and diligent father, factory worker Kwon Gang-Ho supports his family with the little that he earns. At his workplace, he is admired by everyone due to his benevolent nature. Meanwhile, in Seoul, Gang-Ho's wife Yeong-Ran looks after their children on her own. Despite struggling to keep the family afloat, she never neglects her kids and puts in all her effort to raise them.

When Gang-Ho's carelessness gets him involved in an accident, it leaves his face with severe burn marks. Dismissed from his job afterward, Gang-Ho returns to Seoul. However, since he does not want his family to know about the mishap, he decides to stay at his friend's house for the time being.

One day, Gang-Ho encounters his daughter crossing the street. Suddenly, a car speeds forward and almost hits her, but Gang-Ho arrives in the nick of time and rescues her—wearing a mask of the fictional hero "Gugu-man." Following this incident, Gang-Ho starts using the costume of Gugu-man to keep an eye on his family without ever revealing himself. Thus begins the heartwarming tale of a devoted father and his earnest endeavor to protect his family, all while having to face arduous circumstances of his own.