Hyakki Yakou

"Hyakki-Hyakki-Hyakki Yakou! It may be day, but we won't flinch! Let's go! Hyakki Yakou!"

- Hyakki Yakou roll call performed by 100 revived Yokai.

Hyakki Yagyō, variation: hyakki yakō, (百鬼夜行; lit. "Night Parade of One Hundred Demons") is a concept in Japanese folklore which is given a modern envisioning in Shuriken Sentai Ninninger: AkaNinger vs. StarNinger Hundred Nin Battle!.

Overview
"Long ago, during the Heian Age. In the summer, when the Yokai become more active. The legend says 100 types of monsters would rampage on a dark night. Even Yokai that had gone to Hell would revive. They would wreck and pillage the town, leaving nothing left. In other words... it's a Yokai Party Night."

- Hyakki Yakō as described by Kinji Takigawa

Ninninger
The Hyakki Yakou phenomenon, as encountered by AkaNinger and StarNinger, saw the appearance of 100 revived Yokai in the middle of the day as opposed to at night, with Kinji theorizing that Gengetsu Kibaoni's seal being removed caused the Yokai to appear regardless of whether it's night or day. Faced with an army of a hundred Yokai, AkaNinger and StarNinger decided to make a contest of which of the two Ninningers could destroy the most Yokai.
 * Yokai Kamaitachi: Destroyed by StarNinger.
 * Youkai Kasha: Destroyed by AkaNinger and StarNinger.
 * Youkai Tsuchigumo: Destroyed by AkaNinger and StarNinger.
 * 58 Jukkarage: 32 destroyed by StarNinger, 24 destroyed by AkaNinger.
 * 24 Dorodoros: Destroyed by AkaNinger using Secret Sword Kakuremaru.
 * 15 Genin Magerappa: Destroyed by StarNinger using Shuriken's Bat.

With AkaNinger and StarNinger having defeated 50 Yokai each, the two Ninningers were left at a draw until the appearance of a Giant Yokai Gashadokuro. Using the Koromogae Shuriken to transform into incredibly powerful 'Clothes Change' forms, AkaNinger and StarNinger both faced the Gashadokuro without the support of their OtomoNin, determined to make it their 51st. Using their Clothes Change Shuriken, the two Ninningers end up destroying the Gashadokuro together with the combined power of the finisher attacks, leaving them arguing as to who dealt the final blow.