Ahae's husband Sejin is not interested in her as a woman. In fact, Sejin is having an affair with Ahae's beautiful younger sister Ara. Meanwhile, Geon-hoo, who suffered from depression due to work addiction, receives a message from the alumni association informing him of a meeting and decides to attend it. At the meeting, he meets Ahae, his senior and next-door neighbor whom he had a crush on in his childhood. She still has a pretty face and a fantastic body. Geon-hoo approaches her with counseling as an excuse, and Ahae is lonely because of her husband's indifference. As if they noticed each other's loneliness, they spend the night together in a hotel room. In the morning, they try to return to their daily lives, but they couldn't forget the night that they shared and they are back to each other's arms again. Will they be able to return to their normal lives?
A wife's husband is having an affair with her younger sister, and she herself starts an affair with a junior who had a childhood crush on her when they both attend an alumni association meeting.