Old-fashioned taste

A younger man, Hyun-gu, is dating an older woman, Mina, who is his preference. So-hee, who lives with Mina, is also older than her, but while she is dating Seungmo, who has a lot of money, So-hee makes her proposal to Mina to change each other's men and meet her. Then one day, while spending hot time with Hyun-gu, So-hee comes into the house and gets caught...