Jang Mi-ran has been widowed for the last 5 years after her husband died in an accident. She has four kids and is busy all day running a household. Fortunately, her husband's company, Saewang Constructions offered her a part-time job out of special consideration to her plight, so she was able to support her family. As the fiance of the daughter of the chairman of Saewang Constructions, Cho Lee-hwan (actor Lee Chang-hoon) is a rich bachelor in his 30s. When Lee-hwan witnessed Mi-ran husband's accident, he could have saved his life if he had immediately provided emergency treatment. Due to his inaction, he lives with guilt in his heart. One day he finds himself working with Jang Mi-ran on a development project and is reminded of his guilt. He feels compassion towards Mi-ran and treats her nicely but one day he kisses Mi-ran in a brief, passionate moment. This seals his fate to marry the widowed Jang Mi-ran and become the stepfather of 4 kids. The tough Mi-ran and her four kids wear down Lee-hwan, and he tries to run away from the family but Mi-ran tracks him down and he settles back into adapting to life as a stepdad. But gradually, he begins to find the true meaning of family and the satisfaction of being a stepdad and husband, so he decides to live with them.