Once You Do It, You Must Take It Off Unconditionally

You have my boyfriend! The exchange sex of naughty sisters who are attracted to each other’s lovers rather than their current boyfriends.
Due to her sudden reassignment, Ye-seo ends up staying at the house of her older sister, Ye-jin. Although Ye-jin hates the sudden cohabitation with her younger sister, they end up living together happily thanks to the friendship between the sisters. Meanwhile, Ye-jin is troubled by the lack of compatibility with her lover, Kyeong-soo, so she throws him away. However, she feels that it’s a waste to throw Kyeong-soo away because he is still a good man, even though it’s not fun to have him, so she confides her concerns to Ye-seo and tells her to have Kyeong-soo. Ye-jin is also attracted to Ye-seo’s lover, Soo-cheol, so when he came to their house and fix the light, Ye-jin seduced Soo-cheol and ended up having sex with him while her younger sister was away. On the other hand, Ye-seo also calls Kyeong-soo to help her with her computer work, seduces him, and they have sex as well.
The secret sex life of Ye-jin and Ye-seo, two flirtatious sisters who swap lovers with each other, begins.