Hyeon-goo, who has always wanted to try a threesome, proposes this to his girlfriend, Mi-na, but ends up fighting with her. When Seung-mo finds out about it, he goes to Mi-na's house instead of Hyeon-goo and comforts her.

Yoon-jeong and Hyeon-goo are about to get married. The two live with Hyeon-goo's father, Seok-jin, until they find a house for their newlyweds. While Seok-jin is having a good time with her girlfriend Joo-ra and living her daily life, seeing Yoon-jeong gives him a different feeling, and Joo-ra and Hyeon-goo are having an affair without Seok-jin and Yoon-jeong secretly. Then one day... while drinking, Seok-jin hears about Yoon-jeong's family situation, and he tells her that he can help.

Not with her husband or boyfriend, she imagined having sex with someone else. Introducing the stories about maturity trained through having sex with new people.