If That Summer, I Didn't Lose You tells the youth story of Gu Ye and Lin Wan from meeting in high school to reuniting many years later. Gu Ye has always been misunderstood by his classmates at school, but Lin Wan gradually discovers during their time together that he is not the boy others see in their eyes. Starting from one encounter after another, the two gradually become each other's important companionship. As the college entrance examination approaches, they also have to face family, academics, future choices, and the upcoming farewell. After graduation, they drifted apart due to their life directions, and meeting again many years later, the regrets of the past were brought up once more. The people missed and the words left unspoken in those years will eventually lead them toward what choices