He is a tall young adult man with a lean muscular build, shoulder-length spiky hair, and narrow, deep blue eyes with the kanji of "Upper Rank" (上じょう弦げん) and daiji of "Four" (肆し) engraved into them. He has two prominent curved horns on his forehead and cracked markings under his eyes. Aizetsu also has the kanji for "sorrow" etched into his tongue. As a demon, Aizetsu has pointed ears and sharp nails on each finger. He is usually seen wearing a dejected expression on his face.