A videotape received in the winter of 2019 evokes memories of the 20th century. "From now on, you will know everything he does. You can trust me!" In 1999, 17-year-old Bora (Kim Yoo-jung) faces the most important mission of her teenage years (when friendship trumps everything, even love): her friend Yeon-do (Noh Yeon-woo) is going overseas for heart surgery, and Bora must observe Yeon-do's first love and report in real time. "His name is Baek Hyun-jin, he is 181 cm tall, his shoe size is 280 mm, and he likes basketball. He is always inseparable from his best friend." To find out everything about Hyun-jin (Park Jung-woo), Bora sets her sights on his best friend Yun-ho (Byeon Woo-seok). However, things do not go as planned, and Bora is surprised to find that she may have fallen in love.