Eun Ha-Won is a college student. She is a bright girl who wants to be a veterinarian, but at home she is lonely. She is isolated from her family members. Eun Ha-Won lives with father, step-mother and step-sister after her mother died in a car accident. One day, she helps a mysterious old man. The old man suggests to her to live in a mansion and pursue her dream of becoming a veterinarian.

Since than, she moves into the mansion and lives with three cousins Kang Ji-Woon, Kang Hyun-Min, Kang Seo-Woo and their bodyguard Lee Yoon-Sung.

A spirited, smart and nice teenage girl, good at sports, hates her home life due to her new stepmother and stepsister. She dreams of escaping her home where she’s treated as an outsider, and one day she helps out an old man and he extends an unusual offer to her. She’s invited to come live in a giant mansion and attend a prestigious high school, where she gets to pursue her dream of becoming a veterinarian. There are four other inhabitants in this house — three beautiful brothers and one bodyguard — who are stubborn and free to do as they please. She opens their frigid hearts and they become their own little family, and find love along the way.