Mint is a girl who happens to be the princess of the world of dreams and magic. The natural environment of her world is a reflection of the dreams of the people on Earth. It is now in danger as people lose faith in their dreams and let darkness enter their hearts. The environment of Mint's world is starting to wither and die.

On her 12th birthday, after a gala celebration with her father the King and her mother, she agrees to go to the world of humans to try to preserve people's hopes and dreams, and to prove that she has the qualities necessary to be a wise ruler. Her father arranges for her to stay with his sister, Mint's aunt Herb, who runs a gift shop on Earth called "Happiness Shop".

(Source: AniDB)