Dae-su, once a promising taekwondo athlete with ‘incompetent swing kick’ and Mira, who dreamt of becoming an idol, unexpectedly became teenage parents at the age of 17. Now they’re 33 and have a 16-year old son Ahreum. Due to an extremely rare genetic disorder called progeria, Ahreum ages exponentially faster than normal people. Even though he’s just a teenager, his body is that of an 80-year old man’s. Despite all the negativity and hardships in their lives, this tight-knit young family carries on, taking one day at a time. One day, Ahreum’s story is broadcasted nationally via network TV program. He is suddenly thrown into the spotlight, and his normally dull days are now filled with moments of happiness, joy and sorrow?

Soo-hyun comes across magical pills that allow him to go back and forth in time. 30 years to the past, young Soo-hyun meets future Soo-hyun and learns that his girlfriend will soon die because of him. In order to save her, the two Soo-hyuns try to change the past together, but a completely new and unexpected past is formed that leads to a new future.