In winter, a mother and her daughter live together alone. The daughter, a high school student, accidentally reads a letter to her mother and finds out the secret her mother has been hiding all her life.
Yoon-Hee lives with her teenage daughter Sae-Bom. On a winter day, Yoon-Hee receives a letter from Otaru, Japan. Sae-Bom accidentally reads the letter and learns about her mother's first love, which she never spoke about before.