Ajuka Beelzebub

Ajuka Beelzebub, formerly known as Ajuka Astaroth, is one of the Four Great 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 came 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 Triaina 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 Power: As the current Beelzebub, Ajuka is one of the most powerful Devils in the Underworld. In fact he, along with Sirzechs Lucifer and Rizevim Livan Lucifer, is one of the three Devils who are considered Super Devils, with their powers and abilities far exceeding even that of the Four Original Satans, rivaling that of some of the more powerful gods. This was shown when he easily disposed of the Devils of the Old Satan Faction which consist of High-Class and Ultimate-Class Devils (who enhanced themselves through unknown means), all while sitting. Lord Gremory has stated that Ajuka and Sirzechs' immense power made it so that there was no position worthy for them besides being Satans.

Specialized Demonic Power: Due to his interest in calculations, Ajuka had developed his demonic powers to specialize in calculations. His Demonic Powers is so unique that among all the Devils, only Ajuka's Demonic Powers specializes in creation.
 * Kankara Formula : Ajuka's specialized move which has the ability to control all phenomenon using equations and formulas and modify it to make it into a special move of his own.

Master Inventor: Due to his liking of calculations, Ajuka became a successful inventor with the fact that he created the Evil Pieces system that helped repopulate the devils and eventually the Rating Games. He even became the Chief Advisor for the Technology Department. Ajuka also modified Issei's evil pieces to allow the latter the ability to promote anywhere at anytime. After the modification Issei had mentioned that he could work very well with Azazel in inventing though Ajuka discounted this idea basing it on that Azazel likes to create something from another while he himself likes to create something from nothing.

Inventions
Being the Chief Advisor of the Technology Department of the Underworld, Ajuka had created many inventions beneficial to it. The notable ones are below:
 * Evil Pieces: The system used by devils today that allows for easier repopulation where the High-Class Devils reincarnate other beings, notably humans especially one with sacred gears, into devils to create a small group of individuals with high power rather than army of small power.
 * Evil Pieces Scanner: In Volume 12 Ajuka showed a chess board that scans the evil pieces placed on it for any abnormalities when the Occult Research Club visited him to find out about Issei's status through his evil pieces.

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 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 three known Devils to be placed among the ranks of the Top 10 "Strongest Beings in the World", the others being Sirzechs and Rizevim.