Yui has a more masculine appearance. He has dark blue hair that reaches just above his shoulders and blue eyes. He has thick eyebrows which accents his intimidating aura. He wears a green fur hooded jacket with grey fur on the hood, dark blue pants and dark brown shoes with darker brown soles and toes. During his childhood, he wears a simple white kimono and footwear which seems to be made of straw. After calling the power of the nil calculus, it was attached to his chest ever since