As a high schooler, Eun Ha Won (Park So Dam) loses her mother in a tragic accident, and her father remarries. When her cruel stepmother moves in with them, she steals Ha Won’s college funds, leaving Ha Won forced to take on multiple part-time jobs to meet her college downpayment. One day, Ha Won meets an old man who sees her fiery disposition and her no-nonsense personality. Convinced that this is exactly what his three grandsons need, he persuades her to move into a mansion, where she will stay as the housekeeper, with three other young men who happen to be billionaire cousins. There’s a middle cousin and lone wolf Kang Ji Woon (Jung Il Woo), a rebel with a cause with a sad past, who might have shared a moment with Ha Won years ago. Eldest cousin Kang Hyun Min (Ahn Jae Hyun), an arrogant playboy with a penchant for smooth-talking, and a money machine used to getting whatever he wants. The youngest cousin Kang Seo Woo (Lee Jung Shin) is a top singer-songwriter, who is easily the most affectionate with Ha Won. What sort of adventures can come out of living with three dashing, spoiled rich men, and who will Ha Won choose in the end?