Bosomy Younger Sister-in-law

Min-soo and Yoo-ri talk about marriage while they are on a date. Yoo-ri goes back home and tells Jeong-hee about marrying Min-soo but Jeong-hee is shocked as she has a crush on him. She has a drink with Sung-hoon and gets drunk telling him about the soon-to-be married couple. Sung-hoon who has a crush on Jeong-hee, has drunk sex with her. Jeong-hee is confused the next morning and runs into Min-soo who happens to be home. Jeong-hee realizes the fun about sex and slowly starts to be obsessed with Min-soo. Min-soo can't turn her down and Sung-hoon finds out...