One who believes in
Jashin (Literal translation: evil god or evil heart)
Jashinism is a religion practiced by
Hidan of the Akatsuki in Naruto Shippuden. It is highly masochistic and requires Jashinists to inflict pain on themselves every day.
One (and only) known Jashinist is
Hidan of the
Akatsuki.
Hidan: Jashin-sama ("Lord
Jashin" for those who don't know Japanese) will save you from being killed if you convert right now...