A 12th grade student and one of "Two big onee-samas" of the school along with Rias. Called the ultimate "Queen" by other members. Born between a human mother and fallen angel father. After the death of her mother, she became Rias' servant. She is a friend close enough to call Rias by her name in private, yet calls her Buchou in presence of others and displays master-servant relationship in public. She persistently refuses to use her power of light, inherited from her father, starts using it after being convinced by Ise. When fighting she is an extreme sadist.
SpoilerShe admits that she thought Issei was cute from the moment she met him but in Volume 3 she confesses that she's developed feelings for him and begins flirting heavily with him. This starts a longstanding rivalry between herself and Rias in which she jokingly claims that she and Issei are going to have an "affair".