"Hannya" is a female demon belonging to the supernatural world.The hannya mask with its horns and fangs is probably the most well known Noh mask. The mask expresses the fury of a woman that turned into a demon through jealousy and anger.
"Oni" Japanese demons, devil-like demons with long nails, wild hair, a fierce look and horns on their forehead like the devil images known in Western Christian cultures. They fly around and seize the souls of wicked persons on their deathbeds.
I agree with evil, seems like white americanz lack culture, that's why they jock other more exotic cultures style... but I have to admit they did a good job on this tat.