In 2005, Kang Moon-Jae is a high-school student and a trouble maker. Since his mother remarried, he has lived with his father, Kang Ka-Deuk, but he can't get along with him. One day, Moon-Jae runs away on his motorcycle and gets into an accident. He then finds himself in 2015 and learns that his father is in a comatose state. Ka-Deuk got into an accident trying to find his son. Moon-Jae decides to go back to 2005 to change the future.