After falling unconscious, Princess Rong Le (Sophie Zhang) of Western Xi wakes up not remembering anything. In order to form an alliance with Northern Lin, she is to be married to Prince Wu You (Aarif Rahman), but Wu You rejects her. Rong Le thereupon takes on the identity of a teahouse owner named Man Yao and tries to find a mysterious book. Wu You gets to know Man Yao and falls in love with her, not knowing that she is in fact Rong Le. But Rong Le is now already promised to General Fu Chou (Jing Chao).
When We Were Young revolves around twins (both played by Zhang Xue Ying). One is raised by an adopted mother and the other is raised in an orphanage. One twist of fate and a lot of bullying leads the orphanage sister to commit suicide but she’s saved by her twin and they switched identity to solve some mysteries within the school.