Shall we play like adults?

Hye-won, Hee-jung and Joo-hee are university alumni. Everyone is envious of Hyewon who got married first, Hyewon, who has no marital relationship, is more envious of her unmarried friends. Hee-jeong gives her friend Joo-hee, after being proved by Sekpa Min-woo. Hee-jung has an affair with her boss. Hyewon and Joohee discuss changing husband and lover to try. Joo-hee is flirting with Hye-won's husband. Hye-won is attracting Joo-hee's lover. Couples swapping each other and swapping. They break up, promising to meet again.