hyakki_yagyou
百鬼夜行 (Hyakki Yagyou or Hyakki Yakou, literally "Night Parade of a Hundred Demons")
This tag is possibly ambiguous.
For a horde of traditional youkai in the Japanese folklore, demon parade tag is currently used.
For an unofficial series name of Toriyama Sekien's Youkai Encyclopedia tetralogy, just use nihonga tag, or use Gazu Hyakki Yagyou.
For a novel series by Kyougoku Natsuhiko, use Hyakki Yakou (Kyougoku Natsuhiko). Its pixiv tag is 百鬼夜行シリーズ
For a PSP game, use hyakki yakou ~kaidan romance~. Its pixiv tag is 百鬼夜行～怪談ロマンス～