Perhaps the most famous and influential set of classical Japanese monster illustrations is the Gazu Hyakki Yakō series, published in the late 1700's by Edo-ite Toriyama Sekien (1712-1788).

Sekien, whose real name was Sano Toyofusa , was an artist of the Kanō school who had studied under Gyokuen (Kanō Toshinobu). He was born to a family of wealthy Buddhist priests, and became an artist late in his life, seemingly as a post-retirement hobby rather than a profession. Not much of his artwork remains aside from his yōkai drawings.¹

Sekien was a writer of kyōka (satirical poetry) as well as an artist, and the irreverent and pun-loving spirit of the form seems to have had an influence on his artwork. He is mentioned in the writings of his friend, kyōka poet and author Ōta Nanbo.²

Sekien may be best known in the West as the teacher of Kitagawa Utamaro, famous for his erotic images and drawings of women.³ He also had as a pupil Toyoharu, founder of the Utagawa school, which turned out such famous artists as Kuniyoshi, Tsukioka Yoshitoshi, Kawanabe Kyōsai and Katsushika Hokusai - all of whom drew a good number of monsters themselves.⁴

Sekien is further credited with the creation of the fuki-bokashi technique, which allowed for gradations of tone in woodblock prints.⁵

The Gazu Hyakki Yakō series itself consists of four books of three volumes each, containing altogether about two hundred illustrations. Unlike previous hyakki yakō monster collections and processions, which all took the form of illustrated scrolls, Sekien's works were published in book format, similar to the natural history manuals that were popular at the time.⁶ Despite this similarity to materials intended for reference and education, and the fact that many of his monsters were in fact based on Japanese folklore or taken from old texts, more than 80 of them were invented by Sekien himself and others were lifted from older monster scrolls produced by Kanō school arists. ⁷ Many of Sekien's invented yōkai poke fun at depraved monks and the shogunate-approved Yoshiwara red-light district,⁸ making his work less a serious natural history tome and more a grotesquely light-hearted parody.

The books in the Gazu Hyakki Yakō series are as follows:⁹

• Gazu Hyakki Yakō (1776)
• Konjaku Gazu Zoku Hyakki (1779)
• Konjaku Gazu Hyakki Shūi　 (1781)
• Gazu Hyakki Tsurezure Bukuro　 (1784)



Sources:
• Tada, Katsumi and Natsuhiko Kyōgoku . Hyakki Kaidoku (Deciphering the Hundred Demons). Tokyo: Kodansha, 2006. p 247-50.

Citations:
1. p. 18.
2. p. 19.
3. p. 20.
4. p. 23.
5. p. 21.
6. p. 22.
7. p. 22-23.
8. p. 20.
9. p. 18.