Illumi appears expressionless, his face like an emotionless mask. He has very long jet-black hair, usually combed behind his head as well as, very large, dark eyes. Illumi, for the most part, displays very little expression. In contrast to his expressionless demeanor, Illumi often speaks in a somewhat joyful and absent-minded tone. He is generally a stony, ruthless person with an extremely cold way of thinking, reflecting only his interest. He was raised to become an assassin since birth.