There are two type of human being. The first is kakuen, the evolution of primates. The second is madararui, the evolution of certain animals instead of primates.
Kakuen make up only 70 percent of the human population. Kakuen are one animal, but have variety appearance such as monkey and baboon when seeing their soul.
Differences between kakuen and madararui
Unlike madararui, kakuen cannot control the visibility of their own soul's appearance and are not able to see the shapes of other people. Also, kakuen shut out any talk of madararui as though they never heard it. Madararui have various level of fertile and kakuen are very fertile. If one parent is a primate, then the child will be a primate unless it comes out as retrograde, which is extremely rare case. Kakuen believe in loving a single person, while Madararui seem to believe mainly in mating and reproducing their species.
There are three set of level of breeding, which are heavy, light, and flight. Kakuen will always be flight seed, this is the reason why they are very fertile and able to reproduce in large quantity.