Night Class student popular among the Day Class boys and one of the most faithful and protective of Kaname Kuran's followers.
Ruka grew up privileged, as the daughter of a noble family. Her family is part of what is referred to by Asato Ichijo as the "Aido faction", which is comprises of the Kain, Aido, Souen, Toya, and other clans. Not much is known about her parentage, but her father or mother is possibly part of the Senate or in another high position, as Ichio refers to her as "The daughter of Souen". Ruka came to Cross Academy to be closer to her long-time idol, Kaname Kuran, with whom she is "in love" with. On their first night at the school, she asked Kaname to drink her blood to prevent him from drinking Yuki's blood, but he has since refused it, which deeply hurts her, even though she had expected him to refuse her blood.