"Secret Love Affair" tells the story of secret romance between Oh Hye-Won (Kim Hee-Ae), a woman in her 40's, and Lee Sun-Jae (Yoo Ah-In), a man in his 20's.
Oh Hye-Won works as the director of planning for the Seohan Arts Foundation. She is elegant and excels at dealing with other people. Oh Hye-Won becomes involved in a love affair with Lee Sun-Jae. He is genius like pianist in his 20's.