As a high school senior, Su Jeong (Mun Ka Young) began playing an online game where she met another player nicknamed "Black Dragon." They unexpectedly got close, developing crushes and planning a meeting in real life... that concluded in humiliation and disaster when "Black Dragon" turned out to be an awkward middle schooler instead of the young man he portrayed himself to be! Sixteen years later, Su Jeong is a skilled planner at Yongsung Department Store, but her job is about to get a shakeup with the arrival of Ban Ju Yeon (Choi Hyun Wook), the ambitious new head of strategic planning and heir to the company. There's just one problem: Ban Ju Yeon is actually "Black Dragon," and Su Jeong still holds a grudge. Will their past come back to haunt them, or can they find a way to resolve their misunderstandings – and even find love as adults?