Why did Secretary do this

By day, Anne Luo is Michael Fu's dedicated secretary, handling everything from international meetings to his favorite coffee. By night, she's his secret lover. Everyone assumes she'll soon become the "first lady," but only she knows his heart belongs to someone else. The night his "true love" returns, Luo quietly resigns and leaves. Reclaiming her life, she becomes a celebrated designer at Trend Magazine. When she reappears as an investor in Michael Fu's world, the story begins anew.