Rias Gremory

A 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. Kind and soft to her servants, becomes a totally different person when training or fighting. She begins to develop romantic feelings for Issei in Volume 2 of the light novel and moves in with him at the volume's end. In Volume 10, he confesses that he loves her and she returns his feelings. They begin dating after that.