Seon-yeong's husband suddenly loses his job, so a friend introduces her to a sexy substitute driving gig. She hesitates, but decides to do it when she hears it makes more money than an average sub-driver. Then one day, Seon-yeong meets Dong-hoon, the guy next door, while on the job and they have an affair.
This is actually a non-consensual swapping movie, as the main wife's husband is already fucking the neighbor's wife before she started an affair with the neighbor herself. The main wife's first cheating scene is inside the car of her neighbor at 35:50.