Ajuka Beelzebub

Ajuka Beelzebub (formerly known as Ajuka Astaroth) is one of the Four Great Satans in High School DxD, serving as the current Beelzebub and the leader of the Underworld (especially prominent after major events like the Evil Dragon War, where he becomes the sole remaining active Satan in later developments).

He appears as a strikingly handsome and bewitchingly attractive young man who looks to be in his early twenties, featuring slicked-back green hair, light blue eyes, and a deliberately mysterious, enigmatic aura that he himself says makes him seem more "devilish."

Personality-wise, he's a calm, intellectual genius who enjoys creating new things (a rare trait among devils, who are more often associated with destruction). He's a master inventor and tactician, widely regarded as one of the smartest beings in the series.

Ajuka is the creator of the Evil Pieces system (which allows devils to reincarnate others into their peerage) and the Rating Game format. He's a Super Devil-class powerhouse with immense demonic power, specializing in calculation-based abilities — most notably his signature technique Kankara Formula, which lets him mathematically control and manipulate phenomena, laws, attacks, and more. His intellect rivals or surpasses even figures like Azazel in certain fields.