Video : Cinderella and Four Knights

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.