This list of mythical creatures that begin with this letter and I am constantly gathering information from each continent, and is continually being updated.
Hihi (Japanese)
The hihi is a large, monkey-like beast which lives deep in the mountains. It has long, black hair and a wide mouth with long, flapping lips. Old legends say that a monkey which reaches a very old age will transform into a hihi. ihi live primarily in remote mountains and are carnivorous beings that stalk and kill any wild animal they come across, while they do not primarily hunt humans they will attack and devour humans if given the chance and gain their name by the strange "hihihi!" laugh they make upon encountering a human.
The hihi’s origins lie in ancient Chinese mythology, where it was believed to be a supernatural monkey that lived in the mountains. It was brought over to Japan by folklorists during the middle ages. In modern Japanese, hihi is the word for baboon, which takes its name from its resemblance to this yokai.