Nice Sister-In-Law (2015)

Ha-yeong ("Viki") is a successful psychologist. One day she gets a secretive request from her sister, Ha-joo. Apparently her husband Woo-seong is refusing to have sex with her. She agrees to be their couple therapist but during the hypnosis session she finds out that he actually has sexual desires and fantasies for her and not his wife. And they begin a forbidden affair.