Illumi is most often expressionless. He has very long, jet black hair, usually combed behind his head as well as large, black, pupil-less 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 and reflects solely on his own interests. He was trained from a young age to be a professional assassin.