This article is about a villain in Henshin Ninja Arashi.
Majin Sai (魔神斎, Majin Sai) is the head of the Blood Wheel Clan. He has the ambition to control the world by force. For that purpose, he killed Kiju of the Valley, stole the secret technique "Henshin Ninja" from him and used it to create many Incarnation Ninjas. His whole body is encased in Western-style armor along with an iron mask and a black cloak is worn. He wields a metal staff with a sharp tip. Using various spells such as calling thunderclouds, he has the ability to instantly move to the Skull Lair.
In episode 39, he was destroyed by Shinsei Arashi, exposing his identity as a mechanical doll operated by Great Demon King Satan and stopped functioning.