He Ruanruan rides her bike and knocks down the amnesiac Ye Tingzhou. Fearing compensation, she lies that he is her family's adopted older brother. Ye Tingzhou believes it to be true, and in the capacity of an older brother, urges her to study, cooks and paints walls for her, and moves into a new home in the county town. He Ruanruan rises from the bottom student to the top of the grade, and several times wants to confess but is taken as an excuse to escape schoolwork. On the day the college entrance examination ends, Ye Tingzhou suffers a car accident and recovers his memory, yet still acknowledges this younger sister, turning the page on two years of deception.