Lee Young-joon (Park Seo-joon) was a successful vice chairman of a major corporation. He was on top of his career when one day he was blindsided when his dedicated and highly capable secretary, Kim Mi-so (Park Min-young) handed her resignation. After having served him for nine years, he realised that this will take a lot of adjustment because only Mi-so can do what Mi-so does. Young-joon made it a point to do whatever he can to keep her in the company. But along the way he realizes that Mi-so means more to him than just his most trusted employee.