Marathon (Running Boy)

20 years later, Cho-won's intelligence is still that of a five-year-old boy. He farts everywhere, bows to his younger brother, and dances to music wherever he is. However, his mom dedicates herself to training him to accomplish a Sub-3-Hour, which is completing a marathon below three hours, a dream for amateur runners.

One day, Jung-woo, a former marathon champion comes to work at Cho-won's school to fulfill his community service for a DUI. Cho-won's mother begs him to coach her son. Taking the job unwillingly, he learns to open his heart to Cho-won as they spend more time together and sees the possibility of accomplishing a Sub-3-Hour.

Jung-wook and Cho-won's mother have a serious dispute over how to train Cho-won. Amid the heated argument, Jung-wook tells Cho-won's mother that she's obsessed, which makes her realize that she's been pushing his son around to make herself feel better about him being autistic. Consequently, she decides not to let him run any more.