Race: Vampire
Age: 18
Birthday: April 24 (Taurus)
Blood type: AB
School Grade: 3rd year High School Student
Height: 180 cm
Weight: 64 kg
Eye color: grey
Hair color: black
Favourite food: soup
Disliked food: strong-flavoured food and drinks
Hobby: puzzles
Relatives: Kou (Adoptive brother), Yuma (Adoptive brother), Azusa (Adoptive brother)

Ruki Mukami is the eldest son of the Mukami household. He is known as the 'Brains' of the Mukami family. Ruki is a handsome young man with ruffled, short hair colored with black on top and white on the edges. He wears the black web chokers on his neck. He has grey eyes and also three black piercings on his right ear. Ruki has two big scars on his back from when he was a child. He is sometimes seen carrying a book.

He always has an intimidating smirk on his face matched with a calm tone, but a sense of brutality can be felt in his spoken words. Without dirtying his own hands, he interacts with others as a cruel-hearted, military do-S (extreme sadist). Ayato notes that he is an "intellectual" person.