Enigmatic 17-year-old high school student Joo-in is a cheerful friend, a shameless daughter, a mischievous girlfriend, and a person always hard to predict. But more than anything, Joo-in is curious about and baffled by love. One day, some words she says in a fit of anger cause a major scene. Afterwards, she receives anonymous notes questioning her behavior, and cracks begin to appear in her formerly peaceful world. "Joo-in, who is the real you?"