User blog comment:IamJakuhoRaikoben/Chapter 503: The Last Sight Seen, Review./@comment-84.197.239.101-20160926192137/@comment-5303512-20160928143053

All he stated that he has Curse Powers, never confirming that he had magic power to begin with. He also speaks of the powers of the Nine Demon Gates as if they were Curses anyway. Those minor magics are so common they can practically be used by anyone. Even humans can use curses too.

Besides, if somehow Ice Devil Slayer is Magic, then how in the world is Gray suppose to beat END is his powers turn out to be Magic Immunity?