Hyakki Yakō (百鬼夜行; lit. "Night Parade of One Hundred Demons") is a concept in Japanese folklore.
Legend has it that "every year yōkai, the Japanese supernatural beings, will take to the streets during summer nights." Anyone who comes across the procession would die, "unless protected." The children's game Hyakumonogatari Kaidankai was based on this idea.
The night parade was a popular theme in Japanese visual art.
An early example is the famous 16-century handscroll Hyakki Yakō Zu (百鬼夜行図), attributed to Tosa Mitsunobu, is located in the Shinju-an of Daitoku-ji, Kyoto.
Notable other works of this motif include those by Toriyama Sekien (Gazu Hyakki Yakō) and Utagawa Yoshiiku. These works are more often considered "humorous than frightening."
In the Ghibli movie Pom Poko, "Operation Spectre/Operation Poltergeist was intended to evoke the Hyakki Yakō."