Rias Gremory

Rias Gremory (リアス・グレモリー) is 12th grade student and the prettiest girl in the academy. Comes from the old noble of pure devils, the house of Gremory, a top-class devil who is called a genius nicknamed "Crimson Ruin Princess". Her brother is in fact one of the Yondai-Maou, Lucifer. Both of them possess the power of destruction. She revives Issei as her servant after finding him dead, killed by a fallen-angel and possessing a rare Sacred Gear'''. '''Her last name is actually from the real bible where her family name is a a duke sent to hell who commands 26 legions.

Personality
Kind and soft to her servants, she thinks of Issei as special and always gets jealous when girls are around him and becomes a totally different person when she sees him and other girls together, or when it comes to training.

She is proud of her family's name, but she does not like being seen as Rias from Gremory. The reason for her living in human world (revealed in vol 2 of the novel) is because here, everyone sees her as Rias, not as a devil or as the Crimson Ruin Princess.

She enjoy teasing Issei and Asia on purpose (from vol 3 of the novel toward), but at the same time make it clear (to Asia or any girl) that Issei is hers, and she does not want to share him.

The Gremory and their servants are beings with extra-ordinary affection among the devils (revealed in vol 3,life 2), so Rias is no exception. She has no problem with showing Issei her breasts or sleeping naked with him.

Combat Capacity
As a sister of Demon King Satan, the novel hinted that her power is high compare to other Devils at her age. In Vol 1, she and Akeno are able to defeat 3 Fallen Angels. In Vol 3, with a 8 times boost from Issei, she is able to force Kokabiel to defense. Although it is blocked, Kokabiel is not completely unharmed, either.