Eun-joo is a twenty-year-old pre-college student who lives with her sister Eun-hee. Eun-hee is worried about her sister's academics and hires Je-hyuk as her tutor. Eun-joo falls for Je-hyuk as time goes by. They end up making love. A few months later, Eun-joo improves her grades and passes her tests. However, Eun-hee announces that she's getting married to Je-hyuk and Eun-joo doesn't want to lose him...

An Affair: My Sister-in-law's Love

Young Se-hee gets married to middle aged Min-goo, but she's not happy with his 'item' as he's old. While she goes on vacation with her husband, Min-goo's daughter Yoo-jin calls her boyfriend Ji-hoon to the house when her parents are not there and they have sex. Meanwhile, Se-hee comes back home early from the vacation because her husband has to work and runs into a completely naked Ji-hoon.