He's Ours

A woman who had a kid as she did not know who the father was since it was a really drunk one night stand. But she kept the child when she left to America for her job and came back to Korea after three years. A man who is a CEO and did not know he had a child. Of course he had that one night stand but he did not know the outcome of it. Until three years later, she came back and he knew who the woman was, but what he didn't know was that he has a child. What's going to happen to them in the story? Will be a happy ending or a sad one?