Nan-hee finds herself accepting a prize for winning the Spring Literary Contest but it turns out to be a dream as she wakes up from her sleep. In her real life, her mother constantly nags her to quit her job at a publishing company, which doesn’t pay her on time, and urges her to get married. Meanwhile, Nan-hee and Hyung-tae receive an identical text message simultaneously. Nan-hee calls up Hyung-tae after receiving the text message and realizes in mid-conversation that she and Hyung-tae had promised to spend the last day of their twenties together at Mt. Nam, and scheduled a text message to be sent to themselves a year ago to remind them. She tells Hyung-tae to keep his promise and heads to Mt. Nam. Amid other young couples, Nan-hee tries to get Hyung-tae into a romantic mood but it backfires. No sparks fly between them. And that is how they spend the last day of their twenties.