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.

Appearance
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 “creates”, preferring 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 this, 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
A member of the Astaroth clan, Ajuka is Sirzechs's childhood friend and rival. Like Sirzechs, he was 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 system to help replenish the number of Devils which eventually lead to the creation of the Rating Games.

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 the history of the house of Gremory and general knowledge of the Underworld. 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 Pieces to malfunction. He then rewrote the code written in Issei's Evil Pieces to allow his Evil Pieces to adapt to the power of the Red Dragon Emperor. Before going home after altering Issei's Evil Pieces, he asked 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. Rias and the others came to visit him, hoping that he would check on Issei's Evil Pieces and wanting to know if Issei is still alive. The meeting was interrupted 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 thwarting the Khaos Brigade. However, he rejected their offer and finished off the Old Satan Faction with his Kankara Formula, leaving Siegfried to the Gremory Team. He then checked on Issei's Evil Pieces and was interested to find out that four of his eight Pawn pieces evolved into Mutation Pieces, 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 used on Issei.

Powers & Abilities
Immense Demonic Powers: As a Satan and Super Devil, Ajuka is extremely powerful, as shown when he easily disposed of the Devils of the Old Satan Faction which consist of High-Class and Ultimate-Class Devils, all while sitting.

Specialized Demonic Powers: Ajuka has liked calculation since he was a child. Because of this, he developed his demonic powers to specialize in them.
 * Kankara Formula (覇軍の方程式（カンカラー・フォーミュラ）Kankarā Fōmyura): Ajuka's specialized moved 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.

Trivia

 * Ajuka is at the very least over a century old, having created the Evil Pieces System a few hundred years ago.
 * 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 the first three Gundam TV series (Mobile Suit Gundam 0079, Mobile Suit Gundam Z, and Mobile Suit Gundam ZZ). Amuro Ray + Judau Ashita + Kamille Bidan = Ajuka.
 * The only known member of Ajuka's peerage is the "King Snake of the Realm of the Dead", Falak.
 * Ajuka is one of the two known Devils to be placed among the ranks of the Top 10 "Strongest Beings in the World".