A new graduate, Ha-yoon, finds himself reincarnated as the medicinal practitioner Cho-yoon in the martial arts novel, The Returning Hero. Driven by a desire to protect children, he adopts the novel's final boss, a young boy named Seomun Cheon-o, the future leader of the Demonic Cult.

Ha-yoon thinks he's successfully changed the plot, believing he just needs to raise the child well. But then the seven-year-old says, "I want to rip all their heads off."

Is this what it's like to be in the martial arts world? Does experiencing a family's demise automatically turn a child into a vengeance-seeker? Ha-yoon tries to talk the boy out of it, but his body seems to have a mind of its own, blurting out, "Do whatever you want. Create the cruelest martial art in the world or use it to get revenge."

Nothing goes right. His body spouts profound pronouncements, his disciples become fanatically devoted to him, and the little revenge-seeker becomes obsessed with him, refusing to leave his side.