To get his grandfather's inheritances, Oh Sehun has to marry a girl, Im Yoona, who is 4 years older than him. 
She is the grandaughter of his grandfather's bestfriend. He wasn't interested at first, but due to his evil step-mother who always wanted to make the company hers, he finally agreed.
They have to get married and live in the same house, at least for 5 years. Im Yoona wasn't interested too, because she was in a relationship with Luhan. But, for the sake of her father who always believe in her, she agreed to marry him. But, will they get along well?

 200%