Petopeto-san

"Petopeto-san" is a light novel series written by Kou Kimura and illustrated by Yug. The anime adaptation aired from July 9 to October 1, 2005. The story is set in a typical Japanese school, but with one unusual twist: some of the students belong to "specified races," which are inspired by yōkai from Japanese folklore. For instance, a member of the swim team is a kappa, while another student, a nurikabe, can blend into walls and is especially sought after in summer because of their naturally cool temperature.