Issei, Rias, and the club members interact with various groups and organizations, some of which are run by devils who compete against them in sanctioned combat matches called Rating Games, where the characters have been assigned positions akin to chess pieces.
Author Ichiei Ishibumi had previously worked on a horror genre series two years before publishing the first light novel for High School DxD.
In the volume 1 afterword, he mentions that he changed his writing style, and wanted to develop one in the school-life, love-comedy, battle, and fantasy genre.
[LN 2] At the end of volume 4 of the light novels (and the second anime series), fallen angel leader Azazel becomes the club's adviser, and has the girls live at Issei Hyoudou's home.
[LN 1 afterword] Issei demonstrates great potential as his resurrection required Rias to consume all eight pawns of her allotted team.
[S1 ep 9] He can be promoted to use additional abilities associated with higher ranked pieces, either by reaching an opponent's headquarters during a Rating Game, or with the permission of the King.
[LN 17] He also has not-so-serious techniques that he uses against his female opponents including: Dress Break[f] obliterates a girl's clothes after previously touching her;[S1 ep 10] and Bilingual[g] listens to her inner thoughts as if her breasts are talking.
Issei describes her as an ideal Japanese woman with a pretty face that is always smiling, and along with Rias, make up the two great big sisters that are idolized at the school.
[S2 ep 6] After showing Issei her mixed wings, she is concerned he will hate her, but he accepts her, after which she acts more affectionately towards him, saying that she does not mind being third (after Rias and Asia).
[LN 4] Eventually, Issei convinces her to add her fallen angel aspects to her abilities, creating the Holy Lightning attack.
She acquires Fallen Angel Mode (堕天使モード, Datenshi Mōdo), which increases her Holy Lightning abilities, and passes the promotion exam for the middle-class devil rank.
[S1 ep 11] Ishibumi created Yuto to add appeal to the female readers of his series,[LN 4 afterword] and has him develop as the ace of the team as well as a strong backing character for Issei.
[S2 ep 5] Ishibumi purposely gave light novel volume 3 a boy's love–themed title as that story focused mainly on Yuto.
Xenovia later moves into the Hyoudou residence,[LN 4] Like most of the other girls, she is head over heels in love with Issei, even going so far as to seduce him by telling him she wants to make a baby with him because they both have strong genetics.
[LN 4] She reappears in Volume 6 where she joins Xenovia and Asia as a group which Issei calls the "Church Trio" (教会トリオ, Kyōkai Torio).
[LN 18] Voiced by: Ayane Sakura[8] (Japanese); Alison Viktorin (English) Gasper Bloody (ギャスパー・ヴラディ, Gyasupā Vuradi, alt.
[LN 4] His Sacred Gear, Forbidden Balor View[o], lets him freeze time whatever is in his field of vision, but because he is unable to control it, he is sealed in a remote room in the school, and acts as a shut-in.
[LN 16] Voiced by: Rikiya Koyama (Japanese); Phil Parsons[9] (English) Azazel (アザゼル, Azazeru) is the Governor-General of the fallen angels.
[S2 ep 4] In the anime series, he introduces himself as a regular patron of Issei, asking him to accompany him for drinks or to play video games.
[LN 4] Ishibumi created Azazel with the role of a coach, so that he does not participate in Rating Games, and also, along with Yuto Kiba, appeal to the female readers of his series.
In Volume 12, Azazel resigns from his post as Governor-General of the Fallen Angels, which is now succeeded by Shemhazai, and became Grigori's Advisor of Special Technology and supervisor for Issei's town.
[LN 12] Voiced by: Ai Kakuma[13] (Japanese); Mallorie Rodak[14] (English) Rossweisse (ロスヴァイセ, Rosuvaise) is a silver-haired Valkyrie who excels in Norse magic, first appearing in Volume 5 of the light novels, and in the third anime series.
Eventually, after the battle with Loki and Fenrir, Odin leaves her in Issei's town and later gets persuaded by Rias to become her servant, her ranking being "Rook" alongside Koneko, and remains in Kuoh Academy as a teacher.
She is currently pursuing two goals, the first is to create a school to teach devils how to become Valkyries, and the second is to open a discount store that carries everything in her homeland.
Voiced by: Asuka Nishi (Japanese); Brittney Karbowski (English) Ravel Phoenix (レイヴェル・フェニックス, Reiveru Fenikkusu) is the blonde-haired younger sister of Riser and a former member of his team.
Watching Issei fight for the sake of the woman he loves at Riser's engagement party reminded Ravel of her forgotten dream and instilled a desire to understand everything about him.
She is in Koneko's class at school and despite the two of them bickering often (paying homage to the vitriolic relationship between cats and birds, given their species), they are very close friends.
Currently, she seems to be welcoming the feeling of having an actual home and friends, even to the point of not attempting to do any significant damage to Great Red other than kicking him during the time she and Issei were riding his back.
Angels (天使, Tenshi) are the beings from Heaven, which in Ishibumi's DxD world, supports all the religions, including the Church that Asia and Xenovia were part of.
He also said that Issei's "interactions with his perverted best friends [Matsuda and Motohama] are also occasionally good for laughs, as are his own reactions to situations and his amusing alarm clock.