Religion: Followers of Ashurado (Ninjas, worship Shinto demons)
Name: Followers of Ashurado
Other Names: Ashurado Ninjas; Ashurado cult
First Appearance: Wolverine: Soultaker #1 (May 2005): "Chapter One: The Mark of Mana"
Number of Appearances: 3
Enemy of: Wolverine
Type of Organization/Group: warrior
The "Followers of Ashurado" are people who worship the demons of Ashurado. Ryuki is just one of these demons. Wolverine encountered numerous ninjas who were Followers of Ashurado. One of them was named "Heathen."
Based on the multi-issue story in which it appears, "Ashurado cult" (as it has sometimes been called) is probably best classified as a dark sect of Shinto. The Followers of Ashurado are not specifically identified as "Shintoists," however, and they are probably regarded as apostates by normative non-evil Shintoists. Ashurado in this story is identified as the "fourth level of Hell." Because the demons worshiped and the Hell they reside in seem to be part of the overall Shinto belief system and reality presented in this story, the Followers of Ashurado can probably be classified as Shintoists. Because they worship demons, they can also be classified as demonolaters (i.e., worshipers of demons). There is probably also some overlap with Japanese Buddhism as well.
Although Ninjas in comics are often adherents of specific "Ninja sects" or "Ninja cults," and can be classified as religious adherents of Ninjutsu (or Ninpo), it would appear that the Followers of Ashurado (also known as the "Ashurado Ninjas") are not primarily Ninjas in a religious sense. Although this sect utilizes Ninja training and techniques, their loyalty is not primarily given to philosophical Ninjutsu or Ninpo, but to a specific set of demons. Of course, the distinction between this and "Ninja sects" who also worship specific demons may be unclear or arbitrary.
The Followers of Ashurado are not simply people who passively have belief in demons. They actively worship the demons. By following the will of the villainous Hana, the Followers of Ashurado hoped to bring the ancient Ashurado demon known as Ryuki back to power on Earth. It was up to Wolverine and his heroic allies in Japan to thwart Hana and the Followers of Ahurado, lest the demonic forces take over all of Japan and perhaps the entire world.
Suggested links for further research about this character and the character's religious affiliation: