Eighteen Springs

In Shanghai in the '30s, Shu Hui brings together Man Zhen and Shi Jun, and the two fall in love. However, Shi Jun's parents in Nanjing have planned for him to marry wealthy Cui |hi, who instead becomes romantically attracted to Shu Hui. Man Zhen is concerned about the reputation of Shi Jun's older sister, the prostitute Man Lu. After Man Lu marries businessman Hong Cai, he suggests Man Zhen become a concubine and the mother of his children. Man Lu goes along with this plan in order to save her marriage
(Source: Rotten Tomatoes)
~~ Adapted from the novel "Half a Lifelong Romance" by Eileen Chang.