Aidan Kain

"I would give anything to save the world from the Burning Hells and the High Heavens. And if it forever damns my soul to do so, then so be it."

- Aidan Kain Aidan Kain (エイダン・カイン) is the main protagonist of Highschool DXD: The Prime Evil. He is Rias Gremory's second pawn and the host of one of the Prime Evils Al'Diabolos, or known more commonly as Diablo, through the red soulstone he injected into his forehead.

Appearance
Aidan is a tall, slim, well-muscled, and handsome man with black short hair and blue eyes that attracts a lot of girls to him, mostly the 3rd-year females. He wears the usual Kuoh Academy boys school uniform but with black dress shoes instead of the brown ones. His casual attire at home is consisting of a gray tank top, black short sweats, and brown sandals but his public appearance is more casual.

As the Dark Wanderer, Aidan wears a full-bodied cloak to conceal himself when he travels on Earth in disguise. His face is obscurely seen as only a part of his face is revealed with a small red shine on his forehead from the soulstone and red demonic eyes.

When transforming into Diablo, Aidan appears as a hulking brutish red demon beast with black spikes protruding from his back, arms, tail, and head. The red soulstone is shown sticking out of his forehead.

Personality
Unlike his perverted friend Issei, Aidan is regarded as quiet, cold, and strict but is kind and affectionate to others. He will willingly help those in need from trouble and has no problems getting into fights with the males that are jealous of him. While highly knowledgeable and respectable to his fellow classmates, except for the Perverted Trio and other jealous males, he often acts and speaks in a low voice. When he does speak though, he has a down-to-earth personality and focuses on reality and the present while trying not to worry too much of the future or the past. He stays focused with a calm mind in battle, even if it sometimes means he has to go to extreme measures to protect the people he cares for.

Initially, Aidan believed that because he is the host of Diablo itself, he should not be too close to anyone out of fear of hurting them with his power. He is also afraid that because of obtaining such power, he will eventually be consumed by it over time, no matter how much he trains to resist. At one time, he sought to seal himself away so as to not lose control to Diablo and set him loose upon the world. To that end, he detached himself of any emotion until that was restored by Rias, whom he soon fell in love with. He cares for the people around him yet will willingly put people in their place by using the power of Terror to ensure that they do not do something reckless or to reprimand them of their behavior. And unlike Issei who excites himself over the presence of a naked girl, Aidan is not embarrassed and does not mind if a girl(s) like Akeno or Rias sleeps with him or whether they want sex with him.

As Diablo, Aidan is incapable of feeling fear due to his mastery over terror. He is the most creative and farsighted of Rias' peerage and the strongest of her pieces. Calm, cunning, and patient, Aidan sees himself as an artist of terror. He knows that conquest comes when enemies turn their back on fear rather than face them. But Aidan does not acquire satisfaction from conquest itself as he rather feeds on the terror that precedes the conquest. To him, the fear of a victim has/is a greater reward than the pain they suffer when they are actually tortured. As his power increased, Aidan became darker and more terrifying with his words against his enemies, becoming more and more like Diablo.

History
Aidan’s parents were unknown, but he grew up under his adoptive uncle, Deckard Kain, a university religious studies professor who is aware of the supernatural much to the surprise of the ORC. He learned much from his uncle’s writings about the angels and demons, the Eternal Conflict, the Great War, and the Sin War. Along with his uncle, he is a member of the Horadrim, an ancient order of mages created to secretly guard the world from the incursion of the demons with Deckard being the last. While he did not have a hard time growing up, Aidan did not make a lot of friends and was often studying, sometimes looking into his adoptive uncle's scholarly works or working out and training. At some point, Aidan began acquired small handheld crossbows as his main weapon in his travels with his uncle.

Over much of his life, Aidan and Deckard would travel around the world, hunting supernatural artifacts and lore that would help them understand more about the supernatural. Often, they ran into trouble though, mostly from the demons of the Burning Hells that cropped up from time to time while other times were Stray Devils or Fallen Angels. Their travels led them from the papal tombs in Italy to the ancient temples of China, the Mayan ruins in South America to the primitive tribes of Africa, where they found ancient Horadric relics carried by actual members of the Horadrim. Their last stop would be in Kuoh Town, Japan, where Aidan was transferred in as a 2nd year student at Kuoh Academy, unaware that he gained the eye of the Academy's two most popular women.