Petasites japonicus, also known as butterbur, giant butterbur, great butterbur and sweet-coltsfoot, is an herbaceous perennial plant in the family Asteraceae. It is dioecious, with male and female flowers produced on separate individuals. Occasionally, morphologically hermaphroditic (but functionally sterile) flowers exist.
The Ainu people refer to the previous inhabitants of Ezo as the Korpokkur or "people who dwelt below ground"; the name can also be interpreted as "people beneath the fuki", and so they are popularly associated with fuki leaves in art and mythology. More fantastic depictions of the Korpokkur portray them as tiny, fairy-like creatures small enough to use the leaves as roofs or umbrellas.