Marathon tells the story of the relationship between a young autistic man named Cho-Won and his doting mother, Kyong-Sook. Although Cho-Won may be twenty years old, he has only a childlike understanding of the world. He likes chocolate cookies, loves zebras, and can memorize casual conversations and TV shows. He also tends to dance in public and pass gas at the most inopportune times. While these things may seem charming or at read moreleast humorous, this behavior can get him into a lot of trouble due to his inability to understand how the rest of the world operates. Thus, his mother controls many aspects of his life in the name of "protection," a characteristic that will have further relevance to the plot as the film progresses. As a youth, Cho-Won tended to engage in self-destructive behaviors, but with the help of the special school he attends and his mother's insistence that he participate in various physical activities, his condition quickly improved. Believing that he enjoys running, Kyong-Sook enters Cho-Won into a variety of races, and soon decides that her son should compete in a marathon, hoping he'll achieve something every amateur runner dreams of: completing the race in less than three hours. But are these high ambitions for her son's benefit or her own? Does Cho-Won truly enjoy running or has he been "trained" to agree with his mother's demands?