Unlikely Affair summary: 희대의 내연남 / A Man of Great Infatuation / Office Mates The third generation billionaire's secret heir, Dong-Ju X Secret secretary Min-Young.Lee Min-Young of the HR team happened to see Han Dong-Ju, a new employee of the sales team, coming out of the president's office.Surprisingly, Min-Young finds out that Dong-Ju is the president's hidden son.Moreover, he receives a secret offer to spy on his private life in order to make him his heir..."But this new employee, seems like he is flirting with me?!"