Jung Hyuk meets Inju, who was a karaoke assistant in the past, by chance in a neighborhood while she is tired of her married life with Eun Eun.
In-ju witnesses Jeong-hyeok’s affair and catches her weakness and demands money from Jeong-hyeok.
Inju, who needed travel money with her lover Woosung, allowed swapping and the swapping started. Woo-sung and Eun-eun, embarrassed by the proposal of a swapping partner and husband, are forced to swap together.
Then, Woo-sung and Eun-eun are attracted to each other, and they meet each other in secret. Swapping That Dangerous Sex