When her sister's engagement to the Crown Prince is broken off, ducal daughter Francesette is left with no family to look after. Despite her poverty, the ever-positive Francesette makes the most of her baking skills and begins to live at her own pace in the downtown area. One day, she picks up a weak slime on the street. This leads to a proposal of marriage from Gabriel, the Grand Duke of Slime, one of the "Demon Lords"...?