Hanjyuu (半獣) is a half-beast that has both a human and an animal form. They can change between forms at will. As with humans, they are born from the Riboku tree.
Hanjyuu are just as intelligent as regular humans, but are considered less than human in some kingdoms and are given less rights, including school education.
The most famous Hanjyuu in the series is Rakushun, who helps Youko learn about this world.