Untold Scandal (2003)

Based on the novel 'Les Liaisons Dangereuses,' this film is set in aristocratic 18th-century Korea at the end of the Chosun Dynasty. The irresistible temptress Lady Cho asks her cad of a younger cousin, Jo-won, to deflower the innocent young Soh-ok, who is to become her husband's concubine. But, his attentions soon shift to the graceful and aloof Lady Sook, who lives according to her convictions as a Catholic. Jo-won becomes obsessed with seducing this chaste woman who has remained celibate for nine years since her husband's death. However, conquering the most virtuous woman in the land proves to be more difficult than Chosun's notorious playboy expects.

Source: TMDb