Each of us has a memory, which may be deep or shallow, real or illusory.
There is a secret that has been hidden deep in Su Jin's heart for a long time, which is the secret love that ended before it even started.
The man in her memory always loved to laugh. His grades were not very good, but he played the piano well. He had a weird temper, but he could still attract her.
As time goes by, youth fades away, and that young and frivolous love will eventually be broken by reality.
People have to learn to grow, and some people will always leave.
The words in the postcard have since become Su Jin's memory of youth.
'My girl I wish you a happy peace' [My girl, I wish you peace and happiness]