An androgynous voice, though lean slightly more to the feminine side. 

Children born into the Ryougi family are generally male and are artificially induced with dual personalities, but Kaname was unable to manifest a second personality of his own. Shiki was confirmed to display the trait instead and was raised as the family head in his place, displaying the personalities of SHIKI, a male personality customarily called the "yang" personality, and Shiki, the female personality called the "yin" personality.

It is not the result of Dissociative Identity Disorder even though it is a dual personality, so it is more a matter of whose actions take priority. It is easy to tell which Shiki is speaking at a given time because they both have a distinct style of speaking, most notably that the female Shiki speaks politely and with reserve, referring to herself with the gender-neutral pronoun watashi, while the male persona has a brash personality and refers to herself with the masculine pronoun ore. The two personalities could not communicate to each other but they can both understand what the other is feeling. When one comes out it is like the other goes to sleep, and at the moment they switch they feel each other’s desires.