*“I told you I would remember you.”* *“It’s good to see you again, crown prince.”* There is a girl named Kyungmin with a special talent of time traveling in the Republic of Korea in 2020. One day, Kyungmin meets the 18-year-old Prince Gwanghae, who came to the present from the Joseon era. Although it was only for a single day, the two of them leave each other with unforgettable memories. After returning to Joseon, Prince Gwanghae is unable to forget Kyungmin for a long time, and waits for her while dreaming of reuniting with her. And due to her father’s sudden death, Kyungmin carries out a life-threatening time-traveling journey. And there, she meets the 27-year-old Gwanghae.