|This article is about a/an monster class in Kamen Rider Decade.|
The Ayakashi (アヤカシ Ayakashi) are ancient spirits with nightmarish forms that serve the Gedoushu in the World of Shinkenger, dwelling within the depths of the Sanzu River until being summoned to go through the gap. However, they can only remain in the mortal world until they begin to dry up, returning to the Sanzu River to regain their moisture. Each Ayakashi has two lives, the human-sized first life (一の目 ichi no me), followed by the giant second life (二の目 ni no me) after they are slain in their first life.
When the Hikari Studio arrived in the World of Shinkenger, the Ayakashi Chinomanako stolen Diend's Diendriver, turning him into the Rider of a world that initally had no Kamen Riders, presenting a threat to its stability, it also removed his second life. Kamen Riders Decade and Kuuga teamed up with the Shinkengers to destroy this Ayakashi. (Shinkenger Act 20 and Act 21)