Film director Siyeon wants to love forever. But is that really possible? Both eternity and love are infinitely heavy for Siyeon. Then, in a letter from her parents that she found by chance 27 years ago, she sees two people who are convinced of eternal love. Where did the love of Jaesoon and Jaehwan, who dreamed of eternal love, go? Siyeon wants to learn how to love forever by filming a documentary about the two.