Based in 1996, Yang Xi (Wan Peng) is spending her summer break training for a long distance run. One day, she is injured by a lab explosion while chasing a bike thief ruining her chances to compete. When the school year begins, a new transfer student is introduced, Hua Xiao (Hou Ming Hao). He is an intelligent and reliable student with a hot-blooded exterior. But when Yang Xi realizes it's the same culprit from her accident and that he's running for class president, a new rivalry begins. How will daily school life change when a tomboyish girl and a hot-blooded genius go head to head? "When We Were Young" is a Chinese web drama based on the Yan Sheng web novel of the same name.