Oni no Ou to Chigire - Chapter 2 Pg 51

Humans are normally born in nine months, after two months of pregnancy, if there is little growth of the fetus, and there is a substantial delay in the delivery date, but without labor pains, it is known that the child will be a demon master. On the other hand, a child born with a typical gestation period could not become a demon master after the fact. It seemed impossible for someone like Katsumoto to become a demon master, even though he could see demons. If they werent a demon master, they were unable to make contracts with demons, or put them under their command. To demons, humans were considered food, nutrients to amplify their power. Even if a demon were to befriend a human on a whim, when the demon gave into their appetite, that human would be eaten, and it would be over. Since demon masters were humans, they also fell under the category of nutrients, but compared to normal humans, they had special qualities that made them difficult prey. The one who taught him all that was Katsumoto.

A four year old Tokimori was drawing at a small table for children with Katsumoto. There were crayon drawings of demons in various sizes and colors in his white sketchbook. Tokimori didnt want to draw scary demons, but Katsumoto told him, try drawing them, in a voice he couldnt disobey, so he had no choice but to draw them.