My Beloved Sister revolves around a twenty-something woman who is suddenly thrown into the cold world together with her immature brothers, after losing her father to a sudden accident. Within a very short period, she experiences the two extreme facets of life. Coming face-to-face with poverty, something that is more scary and unfamiliar than sadness, she also has to withstand psychological downfall, which is more difficult than her loss of wealth. Fortunately, there is a man standing next to her, quietly supporting her. She overcomes her crisis thanks to this simple, warm-hearted man and his family, finally recovering her original place through her own strength and means. Through the story this young woman and the people around her, this drama series intends to ponder about the true and worthy values that we need to pursue to make our lives more meaningful.