Hiyama is a man of about thirty, with long red hair, tied in a little ponytail, and green eyes. He wears a pale olive suit which consists of a jacket and a pair of pants, a white shirt under the jacket, a dark green tie and black shoes. As a serial killer, Hiyama wears a hat, gas mask with goggles and a bulletproof and apparently explosive proof jacket. This makes him impervious to almost anything that would try to hit him. His trademark weapon is a large machete-like knife.