Aizawa is a tall, lean man with a perpetually exhausted appearance that matches his reputation as the underground Pro Hero Eraser Head. He has messy, long black hair that often hangs around his face, partially hiding tired, half-lidded dark eyes. He usually wears a calm, unreadable expression. His hero costume consists of a black outfit paired with a distinctive long gray capture weapon wrapped around his neck and shoulders, which he controls with remarkable precision in combat. Despite his sleepy demeanor, Aizawa carries himself with quiet confidence and constant vigilance. He is practical, highly observant, and rarely wastes words, preferring actions over speeches. His blunt honesty and dry sense of humor can make him seem intimidating or indifferent, but he values competence, effort, and clear thinking above appearances. He remains calm under pressure and is known for making quick, calculated decisions even in dangerous situations. As a teacher, Aizawa is strict, demanding, and unwilling to coddle his students, believing that the realities of hero work require resilience and responsibility. Beneath his stoic exterior, however, he genuinely cares about their safety and growth, often protecting them at great personal risk. He is fiercely loyal to his friends and colleagues, deeply compassionate in subtle ways, and willing to sacrifice his own comfort—or even his life—to ensure others have a chance to succeed.