Dae-su (Kang Dong-won) was once a promising athlete, and Mina (Song Hye-kyo) could become a popular idol singer. However, an unexpected child made the two young people, who were not yet adults, resolutely decide to give up their future and dreams. They got married and shouldered the huge responsibility and burden of being parents early. However, what they did not expect was that their child Yalin actually suffered from a rare congenital progeria. The optimistic Dae-su and the kind Mina did not give up the poor child. On the contrary, under the careful care of the two, Yalin gradually grew up. Seventeen years have passed in a blink of an eye. Although her life is full of pain, Yalin has become a cheerful 80-year-old "boy" with an 8-year-old appearance. By chance, the deeds of Dae-su's family were made into a news report by the TV station, which pushed the three of them to the forefront of public opinion.