He vowed to divorce that manner less girl, the moment he put the wedding ring on her finger. After completing his PhD, the billionaire heir of Korain Enterprises, was ready to take the position of the youngest CEO in South Korea. However, the murder of a student in the prestigious Korain University, made Tae-won Lee go undercover as a first-year undergraduate student. There he encountered Gyuri who is the sole witness of the probable killer. Due to a misunderstanding, a hate relationship between Tae-won and Gyuri as both are willing to go to any extent to defeat the other. On the other hand, Gyuri saved Tae-won's grandfather during a medical emergency and to pay his debt of gratitude, Tae-won is ordered to marry Gyuri. But this marriage is a family secret unknown to the rest of the world. Will Tae-won and Gyuri survive their married life? What will Tae-won do when he discovers that the killer's next target is his wife, Gyuri?