Friend Couples: Swapping.

I'm sick and tired of doing it with the same person! We've already seen everything; why don't we swap? Seon-joo and Jae-yong and Tae-gyun and Ga-hee are two married couples from the same university. They go on a trip together and get drunk and talk about the good times they had and the times they had sex with each other's husband or wife. At first, they felt jealous over this but from some point on, they dream of something exciting once again.