This list of mythical creatures that begin with this letter and I am constantly gathering information from each continent, and is continually being updated.
Kokakucho (Japanese)
It is normally seen in bird form, but it is said to be able to take off its feathers and become a human woman. A man who steals the feathers can make her his wife. In Japan, the kokakucho is a bird-like ubame, a Japanese spirit of a woman who died delivering a child without providing care for her baby.