Rein is a tall, well-built, and cool-looking man. He has messy, ash grey hair along a black mesh with bangs in front of his forehead and blue (green in manga and anime) eyes. In light novels, he wears a half black and half grey shirt with folded sleeves, a brown belt around his waist, which has a pouch for his ammunition or certain items, light black pants with the grey blazer tied around his waist and a pair of leather boots. He is equipped with a body leather armor on his left side.