The Mysterious Men are demons from Hell that are a common enemy in Fear Effect. The black-clad variation appears in the fishing village whereas the red-clad variation appears in the depths of Hell itself.
These minions of hell come in two variations, one dressed in black wearing a white kabuki mask, and one dressed in red wearing a skull and crossbones. Both variations have clawed hook hands made of iron. They speak in a dual voice that sounds like a male and a female talking together. They usually attack in groups, appearing for a moment and then warping to another part of the screen, getting closer and closer each time they warp. Once close enough, they charge forward and make a three handed swipe with their hook hands. The red-clad men are stronger than the black-clad men.
Pay attention to their teleportation patterns. Do not let them get close. Move around as needed so as to avoid direct contact and try to shoot them from a distance. At times they will warp right in the middle of being fired at, with the bullets doing no damage. It's a good idea to fire in burst shots because of this, as it will conserve ammo.