After losing her mother in a tragic car accident, nine-year-old Melmo Watari now faces a big challenge: taking care of her two younger brothers, the preschooler Totoo and baby Touch.

Watching from Heaven and concerned about her kids' terrible situation, their mother decides to appear in their lives one last time as a ghost and give Melmo a jar full of magical candies. The candies have the power to make her 10 years older or younger, as well as turn her into any animal she wants. Using her newfound abilities, Melmo wears various disguises as a 19-year-old woman and looks after her brothers, all while still trying to lead a normal life.