In 1999, Yong studies mechanical engineering at a university. He first entered the school in 1995, but took time off to perform his mandatory military service. After finishing his military service, he came back to school as a student. His first love is Han Sol. Yong then somehow communicates with Mu Nee. Mu Nee lives in the present day. She enrolled at her university in 2021 and majors in sociology. Yong and Mu Nee, who are from different time periods, communicate and their story unfolds.