Ajuka and Sirzechs have a long relationship, being childhood friends and rivals. The two of them were the aces of the Anti-Satan Faction and both rose to become Satan's after forcing the Old Satan Faction to retreat. While his relationship with Sirzechs may seem to be bad due to their differences in ideology, their friendship is without a doubt a very close one, as he told Siegfried that the reason why he can concentrate on his hobbies is because of the fact that Sirzechs includes all of his will and further states that the only man he can call "friend" is Sirzechs.
Serafall and Ajuka are shown to get along well with each other, with Ajuka allowing Serafall to call him "Ajuka-Chan".
Falbium and Ajuka are shown to get along well with each other, they also work together when in need like during the crisis of the Underworld caused by the Jabberwocky and Bandersnatch.
How Ajuka and Diodora are related is unknown and what kind of relationship they had if there was one, but Ajuka did not seem to care much about Diodora, as Ajuka did not show interest about the event of his relative's alliance with the Khaos Brigade, nor his death.
Ajuka first meets Shiva in Volume 20, where they play a game of chaturaji in the Fallen Angel's territory. Ajuka converses with Shiva about 666 and gives him a warning to not hinder Sirzechs and not to cause destruction upon the world. Shiva finds Ajuka amusing, knowing that all mythologies fear him more than Sirzechs, but he does not.
For unknown reasons, Tiamat is indebted to Ajuka and she become his secret judge for the Rating Games.