Ajuka Beelzebub

Ajuka Beelzebub, formerly known as Ajuka Astaroth, is one of the Four Satans. He is the chief advisor for the technology department, and is the creator of the Evil Pieces system and the Rating Game.

Appearence
Ajuka is a handsome young man with a mysterious aura which he claims makes him seem devilish.

Personality
Ajuka is a rare person among devils who “create”, prefering to create new things and claiming that it is one of his hobbies. Ajuka, however, doesn’t care much about the role as a Satan. Despite so, Ajuka isn't irresponsible, proven when he kills the Devils of the Old Satan Faction and creating a method to defeat the Jabberwocky and Bandersnatch to protect the Underworld.

History
Ajuka is Sirzechs's childhood friend and rival. Like Sirzechs, he is also an ace of the Anti Satan Faction and became a Satan after the conflict between the Old Satan Faction and Anti Satan Faction come to an end. Sometime after being a Satan, Ajuka created the Evil Piece that eventually lead to the creation of the Rating Game.

Birth of the Breast Dragon Emperor
He first appears in Volume 5 along with the other Satans during the opening ceremony for the Young Devils Gathering.

The Heroic Oppai Dragon
In Volume 8, he participated in Issei and Rias' ceremony at the Ruins of Connection, where he acted as Satan Blue and tested them on table manners. After the ceremony, he decided to have a look at Issei's Evil Piece after learning that the original program written by him was overwritten by a different code which he speculates to be the effects of the Juggernaut Drive but was in a messy state that could cause the Evil Piece to Malfunction. He then rewrote the code written in Issei's Evil Piece to allow his Evil Piece to adapt to the power of the Red Dragon Emperor. Before going home after altering Issei's Evil Piece, he ask if Issei is interested in playing in a new "game" he developed which Issei refused.

In Volume 12, Ajuka was in the human world preparing a method to defeat the Jabberwocky and Bandersnatch that are attacking the Underworld. While Rias and the others come to visit him hoping that he would check on Issei's Evil Piece wanting to know if Issei is still alive. The meeting was interupted by the arrival of Siegfried and the Old Satan Faction who attempted to form an alliance with him. It was also revealed that the "game" he mentioned in Volume 8 involved with thwarting the Chaos Brigade. However, he rejected their offer and finishes off the Old Satan Faction leaving Siegfried to the Gremory Team. He then checks on Issei's Evil Piece and was interested to find out that four of his eight Pawn Pieces evolved to Mutation Piece, which he speculates to represent the Trident and Cardinal Crimson armor. After checking the Evil Pieces, he gives assurance to the Gremory team that Issei's soul is alive and still has his Sacred Gear with him while telling the team that the Evil Pieces can still be use on Issei.

Powers & Abilities
Ajuka has liked calculation since he was a child. Because of this, he developed his demonic powers to specialize in them. He has a technique called the Kankara Formula (覇軍の方程式（カンカラー・フォーミュラ）Kankarā Fōmyura, lit. "Equation of Military Supremacy"), which has the ability to turn every phenomenon into equations and formulas and control it to make it into a special move of his own, there by increasing its speed and power. He is extremely powerful as revealed in Volume 12 when he defeats the Devils of the Old Satan Faction that consist of High-Class and Ultimate-Class Devils, all this while sitting. It is also revealed that of the current Satans, only he and Sirzechs have surpassed the previous ones and are known as Super Devils.

Trivia

 * He claims that he became a Satan because Sirzechs became one himself.
 * His name is made from combining the first syllable of the names of three protagonists from different Gundam series (Mobile Suit Gunfam 0079, Mobile Suit Gundam Z, and Mobile Suit Gundam Z). Amuro + Judau + Kamille = Ajuka.