Voiced by: Yōko Hikasa (Japanese), Jamie Marchi (English)^[1][2]

Rias Gremory (リアス・グレモリー Riasu Guremorī^?) is the heroine of the series. She is a third-year student at Kuoh Academy and the Academy's number one idol, and is known as one of the "Two Great Ladies" (駒王学園の二大お姉さま Kuō Gakuen no Nidai Onee-sama^?) alongside Akeno. Known as the Crimson-Haired Ruin Princess (紅髪の滅殺姫（べにがみのルイン・プリンセス）Benigami no Ruin Purinsesu^?, lit. "Crimson-Haired Princess of Destruction") and the Princess of Destruction (滅殺姫 Mezatsu-hime^?), she is the heir to one of the highest-ranking and famous Devil families, the Gremory Family (グレモリー眷属 Guremorī-kenzoku^?). She earned the nickname because of her family's trademark crimson red hair, and is able to use the Power of Destruction by inheriting it from her mother, Venelana, who is a descendant of the house of Bael before becoming a Gremory through marriage.

She is enrolled in Kuoh Academy as an exchange student, but the truth is that she holds the power in the Academy, and acts as the President of the Occult Research Club which is made up of the Devils under her command, and her rank is "King". This is why they can use the club room (which is the old school building of Kuoh Academy) after dark while the Student Council is in charge during the day and keeps things running smoothly and peacefully. However, in addition to getting high scores at the school she also has to do homework, projects and assignments to receive credits at Demon School. This is required because a special exception was made for her and her servants to attend a human school. If she does not maintain her grades and credits at Demon School, the whole club will be sent to the Underworld to attend Demon School.

She is an invincible heroine who saw the power sleeping within Issei, and took a curious interest in him. To her dismay, the character Switch Princess in Oppai Dragon was based on and looks just like her, and is called the Crimson Bust Princess (紅髪の魔乳姫（クリムゾン・バスト・プリンセス） Kurimuzon Basuto Purinsesu^?, lit. "Crimson-Haired Magic Breast Princess") by Azazel.

In the light novels, it is revealed that her brother is, in fact, one of the Four Maous, Lucifer, and both of them possess the Power of Destruction that was inherited by their mother, who came from the House of Baal, which are famous for that power. She revives Issei after the latter was killed by the Fallen Angel Raynare, and becomes his master. She is both kind and soft to her servants, but becomes a completely different person when training or fighting. She is proud of her family's name, but she does not like being seen as Rias of the Gremory Family. The reason she wants to live in human world is because there, everyone sees her as just Rias, not as a Devil or the heir of the Gremory Family or as the Crimson-Haired Ruin Princess. It is also because of this reason Rias has rejected her engagement with Riser.

As the series progresses, Rias begins to develop strong feelings and eventually falls in love with Issei, which becomes more obvious after Issei defeats Riser, and becomes very jealous when he is surrounded by other girls. She moves into his house after Issei defeats Riser to end their engagement. Much later, Issei finally gets the chance to use his Booster Gear Gift power on her breasts, which gives her the ability to shoot "Oppai Beams" from her breasts from then on. These beams can replenish Issei's stamina and energy with every shot. While this does not seem to drain her energy or stamina, there is a side effect of her breasts shrinking with each shot so she won't be able to fire any more beams once she's flat. Fortunately, her breasts will return to normal after a good night's sleep. It is unknown if Akeno or the others would be able to shoot the beams as well, as Rias is the only one whose breasts have received the Booster Gear Gift.

At the beginning of Volume 10 of the light novels, Rias' mother, Venelana, encourages her to push her relationship further with Issei (in which Rias would attempt to seduce Issei), but gets upset when Issei could not call her by her name. At the end of the same volume, Issei finally confesses and calls her Rias for the first time instead of President (部長 Buchō^?, lit. "Club President"). She cries tears of joy and tells him that she feels the same way and the two officially become a couple. Though it seems none of the other girls (Akeno, Xenovia, Asia, Koneko, Irina, and Ravel) have given up on Issei. She has also shown more tolerance towards Issei's dreams of becoming Harem King, even allowing everyone to make dates with Issei at the end of Volume 12 with the understanding that he will always return to her afterwards.

In Volume 14, Rias mastered a new finishing attack during her training with Akeno. She later leaves for Romania with Kiba and Azazel to know more about Gasper's ability.

Salam saya, Rias Gremory

REFERENSI :

http://en.wikipedia.org/wiki/List_of_High_School_DxD_characters