A former arm-wrestling champion raised in the U.S. returns to South Korea for a tournament that could return him to glory, but he finds his life complicated by the appearance of the biological family he never knew.

A story of how Park Kang's life is changed on Christmas day. Park Kang is a popular actor, but he is also a scandal maker. His manager is Jo Yoon and they are also long-time friends. One day, Park Kang's ex-girlfriend Soo-hyun suddenly appears in front of Park Kang.

Along with his young son, Ji-ho, Woo-jin misses his wife Soo-a, who died after promising to return a year later with the rainy season. Miraculously, they reunite with Soo-a when the rainy season comes around, but she has no memory of her husband and son whom she dearly loved.