Han Jun-hee accidentally traveled back to 1998 from 2023 while listening to music. She meets Nam Si-heon, who looks exactly like her deceased boyfriend. At the same time, she also became good friends with Si-heon's friend Jung In-gyu.
Jun-hee, who has a lively and cheerful personality, travels into the body of gloomy Min-ju, which also makes the lonely Min-ju start to open up her heart. Min-ju's parents often quarreled, and when they discussed the topic of divorce, they usually focused only on her younger brother. This made her very sad, but fortunately she could now confide her grief to a good friend. After Jun-hee traveled through time, Min-ju, who lost control of her body, was trapped in her heart. Her face, body, voice and memories were all shared with Jun-hee! Min-ju tries to pretend to be Jun-hee and take back control of her body so that she can get the care of her family and friends! But she found that everyone liked Jun-hee
Through Min-ju's handwriting and her appearance in the rain, Si-heon realizes that she is not the Jun-hee she knew before, and gradually begins to avoid her! No one wants Min-ju to go back to being the loner she used to be, including friends and family. She has been rejected by all kinds of people and feels that only after death can she become the Jun-hee in her mind. Jun-hee and Si-heon said goodbye at the beach. Si-heon promised that he would never forget her and that no matter what method he used, he would find her in the end. Sure enough, she met Jun-hee when she was a child. And he worked hard to get into Jun-hee's university. They later fell in love, but their love was doomed to tragedy from the beginning.