 A kitsune may take on human form , an ability learned when it reaches a certain age — usually 100 years , although some tales say 50 . As a common prerequisite for the transformation , the fox must place <unk> , a broad leaf , or a skull over its head . Common forms assumed by kitsune include beautiful women , young girls , or elderly men . These shapes are not limited by the fox 's age or gender , and a kitsune can duplicate the appearance of a specific person . Foxes are particularly renowned for impersonating beautiful women . Common belief in medieval Japan was that any woman encountered alone , especially at dusk or night , could be a fox . Kitsune @-@ <unk> or fox @-@ faced refers to human females who have a narrow face with close @-@ set eyes , thin eyebrows , and high <unk> . Traditionally , this facial structure is considered attractive , and some tales <unk> it to foxes in human form . <unk> on the theme have the kitsune retain other <unk> traits , such as a coating of fine hair , a fox @-@ shaped shadow , or a reflection that shows its true form . 
