In an era where social media connects people all over the world, high school senior Seongsil has maintained a decade-long penpal friendship with Jessie—a friend she's never met in real life. Stressed out by college entrance exams, Seongsil impulsively suggests meeting face-to-face, and to her surprise, Jessie eagerly agrees to visit Korea. On the day of their long-awaited meeting at the airport, Seongsil expects to find a girl in a yellow hoodie, just like she imagined. But when Jessie arrives, Seongsil is shocked to find that Jessie is a boy! How could the Jessie she knows be a girl in the same grade, yet the person before her is a guy?