Endless Rain (2021)

This is a story about waiting." Young-ho (Kang Ha-neul), who was living a boring life without any clear dreams or goals while studying for the university entrance exam for the third year in a row, is reminded of a cherished friend from his childhood and decides to write her a letter. So-hee (Chun Woo-hee), who hasn't found her own dream, runs a bookstore with her mother. One day, she receives a letter from Young-ho that had arrived for her sister So-yeon who is extremely ill and in the hospital. So-hee replies to Young-ho on behalf of her sick older sister, and the two continue to correspond through letters.