In July 2012, at the 38th class reunion of Gwangan High School in Busan, 33-year-old Cheng Si-won (played by Jung Eun-ji), who has been working as a TV writer for 10 years, and his former friends recalled their high school days full of youthful restlessness. Surrounding Shiyuan's family and her friends, the curtain of memory unfolds in the intertwined narratives...