Son Ye Jin as Park Kae In
Park Kae In is a clumsy, innocent girl and easy to trust everyone around her
Lee Min Ho as Jeon Ji Ho
Jeon Ji Ho is a charismatic, stubborn and competitive person. Jeon Ji Ho is also a spotless and tidy person. He dreams of being a successful architect and would do anything to get the best design for winning the competition. On the other hand, he has a pure heart and a caring personality. He is put in charge of taking care of Park Kae In in her difficult situation as a roommate and ends up becoming her boyfriend.