Yeong-tak and Ha-na are stepsiblings who live with the support of their divorced adoptive parents. The two begin taking individual private lessons for their respective careers. Yeong-tak secretly gives his acting teacher Na-ri sleeping pills to covet her body, while Ha-na is busy seducing her physical education teacher Han-cheol. Meanwhile, Na-ri and Han-cheol run into each other at the stepsiblings' house, fall in love at first sight, and seek revenge on the two who offended them.
Sisters Ji-soo and Ji-yeong decided to sell their used underwear due to financial difficulties. Perverted men offer to buy them at a higher price by asking these two sisters for shots of them wearing the underwear. Other men offer to pay even higher prices by demanding sex out of greater desire. As the sisters earn more money than expected, their service becomes more and more popular.