Jae Kyung, Yeol Mae, and Yun Hee are three inseparable friends. Yun Hee is married to Taek Su. In Ku is Jae Kyung's boyfriend, and Bong Chul is Yeol Mae's boyfriend.

Taek Su is having an affair with a fellow co-worker, which his wife finds out about. Yun Hee decides to find her own success in the workplace rather than live as a homemaker for her husband.

In a competitive businessplace, Jae Kyung wins a high position, but her superior, Jang Su tries to sexually harass her. When In Ku found it out, he got angry, but kept the story quiet in exchange for the position that Jae Kyung had gotten. Jae Kyung, feeling betrayed, moves to a another city to work as a supervisior, where she meets Sin Ho, who works as a manager there. Sin Ho is a warm-hearted guy that falls for Jae Kyung.

In Ku, though, is not a guy crazy for ambition, but has his own dark family secret, connected to the company's president, Lee Soon Jae which is why he wants to succeed in that company. This yearning for recognition constantly puts him in a dilemma where he has to decide whether to get his success or Jae Kyung.

Bong Chul is an unemployed 'bum' that always uses money that innocent Yeol Mae gives.

In the beginning of the drama, guys defined a 'bad girl' as a girl that is sexy, smart, and cute because they are hard to control, but the drama tries to redefine the stereotypical images of career women.