Shin Soo Yun

A sexual scandal between a math teacher and a student in a prestigious high school ends in tragedy. Four years later, they meet again, now both adults, to reveal the corruption in school and to regain one's reputation as a teacher. Ji Yoon Soo is a high school math teacher with a bright smile and a positive impression of others. She is a hard-nosed and stubborn person who has to push ahead with the decisions she has made. She is a math geek who loves solving difficult problems and teaches students to purely love math. Baek Seung Yoo is emotionless and has no light in his eyes. He used to be a math genius who appeared on a quiz program at the age of five and surprised the world by solving college-level math problems. He was admitted to MIT at the age of 10 but dropped out at the age of 12, and suddenly disappeared. (Source: CJ ENM)

Hwang Tae Hee is the daughter of a chaebol and a team leader at her workplace. She is married to Bong Joon Soo, who works at the same company. When Bong Joon Soo's ex-girlfriend, Baek Yeo Jin, who happens to be Hwang Tae Hee's rival as well, begins to work in her team, troubles start to surface. Tae Hee has to juggle her challenges in love with those at work, helping shape her boss and department director, Goo Yong Shik, from an insensitive and uninterested second-generation chaebol to a true leader. Tae Hee's seeming success in love, however, presents her with another problem as she begins to realize that marriage involves just as many obstacles to overcome.