Yōkai have been classified in a variety of ways throughout history, as have the developing cultural views toward them. The classification of yōkai serves as a way to cope with the unknown, preserve culture, and create art. Nonetheless, the taxonomy of yōkai is forever changing.

Historically, Yōkai served as a way to relieve Japanese people of dissonance in their rationality and reality. It is thought that fears and anxieties were the first manifestations of yōkai (Exploring the Thrill of Japanese Folklore 6:38). During the Edo period (1603-1867), there was a significant shift in how yōkai were portrayed. Where they once were persevered by folk tales and word of mouth, yōkai began to be classified and documented. 

Toriyama Sekien (1712-1788) was a key figure in the categorization of yōkai, and his catalogs combined a wide range of yōkai and stories into easily accessible reference points (Shamoon 277). Sekien's work helped to standardize and cement the knowledge of yōkai, the encyclopedic method of organizing material being critical to this process (De-Mystifying of Yōkai). Yōkai were increasingly documented in encyclopedias and literature, making their stories and traits more widely known.