After spending his first day back to school in utter shock, Bok Su tosses and turns throughout the night thinking of Soo Jeong and about what happened between them in the past. Soo Jeong is also sleepless thinking of Bok Su's unexpected comeback as her student. The next day, Bok Su calls Soo Jeong to follow him up to the school rooftop to wind back time and resolve what happened in the old days. (thetvdb.com)