Hentai magazines are fiction and fantasy, literal pornography. It is spiritual garbage and should be avoided just like 50 shades. You remember the old addage “you are what you eat”? Well you are what you consume. If you make a habit of consuming trash (pornography, bad music, blasphemous art, etc) eventually your spiritual health will be trash. If you consume good things (like scripture, good literature, good music, actual art, etc) eventually your spiritual health will be healthy.
Comparing violent movies to pornography is inncorect. Violence and the “thrill of the kill” is a completely different capital vice from the lust that one feels when consuming pornographic material. Remember, sins of the flesh are the easiest sin to fall into and leads us away from God the most. Hence why Baalam enticed Israel with sex and food in order to get them to stray away from God in the book of Numbers.