Han Jun Hee's boyfriend Koo Yeon Jun died one year ago. She still hasn't gotten over his death and misses him a lot. One day, she somehow travels back in time to the year 1998 and finds herself as high school student Kwon Min Joo. There, she meets high school student Nam Si Heon. She is surprised to see how much Nam Si Heon resembles her late boyfriend Koo Yeon Jun.