Shall we swap?

Sinopsis Film

Ji-hee and Na-hee are older sisters. Her younger brother Na-hee is dissatisfied with her boyfriend's poor sex these days. After hearing this, Ji-hee, the older sister, makes a strange proposal to change partners. The next day, Ji-hee begins to actively listen to her brother's boyfriend. Meanwhile, Na-hee visits her brother-in-law's workplace, drinks together, and insists on going to a motel by car...