Song Hye-kyo as Doctor Kang Mo-yeon
A cardiothoracic specialist who works at Haesung Hospital. She is woman who has great abilities. She believes that competence overrules connections but is hit by the harsh reality that she cannot go anywhere without any connections. She is a woman with principles and doesn't fall prey easily to her emotions. Overall, she is the complete package - her speaking abilities are unrivaled, and she is not afraid to admit her mistakes.