Wonyoung's parents died in car accident when she was 2 years old. Her both grandparents take care of her since then. But that wasn't last long. Chaeyeon is her mother's best friend took care of her as both their grandparents too old to rise her. Chaeyeon would bought whatever wonyoung's need, give her a home and take care of her like her own child. Until someday, she realised that child acting weird around her often.