Undercover Miss Hong

Set in the late 1990s, Hong Geum Bo is in her 30s and is an elite supervisor for the Financial Supervisory Service. She is a cool-headed, working woman who only thinks about her job. She goes undercover as a 20-year-old high school graduate, Hong Jang Mi, and begins to work for a securities company where suspicious flows of funds are detected. There, she meets Sin Jeong U. He is the new CEO of Hanmin Securities company.
Sin Jeong U is a natural-born management consultant and a corporate raider who believes that only numbers are honest. He uses any means necessary to reach his goal. He meets Hong Jang Mi, whose face is the same as Hong Geum Bo's, whom he once loved. They become complicatedly entangled.
(source : mydramalist)