Affair (2016)

Soo-yeon lives a dull and boring life daily because her husband is always busy with work and goes fishing when he is not working. One day, Soo-ji, one of her high school friends moves to the house next door. When Soo-yeon happens to watch sneakily Soo-ji and her husband Sang-min having sex, her desire becomes so strong that she becomes to have hard time trying to suppress it. Soo-yeon ends up having passionate sex with Sang-min one day when Soo-ji is away on a business trip.
That night, as Soo-ji spots Soo-yeon and her husband getting out of a car together and her husband being sweet with her, Soo-ji becomes suspicious of an appropriate relationship between the two. Next day, when Soo-ji asks Soo-yeon to meet her outside, Soo-yeon reveals a shocking story to her.