Yuna was born without knowing who her mother is. Her father gets married with a rich woman in Seoul and has his new family. Yuna has grown up and lived with her grandma who's her father's mother in Busan. No one ever tells her about her mother. She has no clue at all, not even a photo of her mother. She doesn’t even know if she is still alive or not. She isn't told anything about her mother or past at all so she doesn't know what has happened in the past.  Everyone including her grandma and father are trying to hide it from her. That’s why she has a commitment to find out who her mother is.

On her last year at high school, her grandma passed away, so her father decided to take her to live with him and his family in Seoul. He has two little sons and one daughter, Yuri who is 3months younger than Yuna. Her father’s family really hates her because her father didn't abandon her even he married with his wife. Since she has entered this house for the first time, she can feel that her life is going to be in hell but she has no choice and she doesn't want to refuse her father's purpose.....