Kami-no-Sei (紙の精 Kami-no-Sei, lit. Paper Spirits) are spirits summoned through Paper Magic.
The Kami-no-Sei take on the form of whatever their summoner desires.
In the 1971 anime, Qi made them take the forms of generic monsters. The first one has a face of a man with light blue skin, pointy ears, wild black hair, and a teal fish body. The second has a vulture head with a yellow beak, light blue skin, white neck feathers and a gray serpent body. The third is a large, dark magenta reptilian creature, with clawed hands, hoofed-feet and a light blue underside. The last is a large spherical being with black hair covering its body, leaving its eye exposed.
Since the 1985 anime movie GeGeGe no Kitarō: Saikyō Yōkai Gundan! Nippon Jōriku!!, Yōjin has appeared as a prominent example.
They are loyal to their summoners.
Witnessing Kitarō and his allies approaching his castle, Qi summoned the Kami-no-Sei to attack them. Kitarō's Hair Needles passed right through them, forcing him and the others to flee the Kami-no-Sei and retreat into a cave. When Nezumi-Otoko mentioned that they used to be paper drawings, Kitarō realized that's why his Hair Needles had no effect on them and summoned Tsurube-Bi to incinerate them.
In the trailer and a poster for the movie, some of paper spirits seen in the manga were seen as well.
Paper Physiology: They are spirits summoned through paper drawings, as such they are unaffected by Kitarō's Hair Needles. However they are also easily susceptible to burning from fire and dissolving from water.
Hair Needles (髪の毛針 Kami no Kehari): Gahi's Kitarō copies are able to use the Hair Needles technique, making their hair as hard as steel and fire them out like bullets.