Kenpachi Azashiro (アザ史郎 剣八, lit. Azashiro Kenpachi), formerly called Sōya Azashiro (アザ志郎宗谷, lit. Azashiro Sōya), is the former 8th Kenpachi of the Gotei 13 and the previous captain of the 11th Division. In order to gain the title of Kenpachi, he slayed the previous one, Kenpachi Kuruyashiki, with his Bankai. He gain this title for unclear reasons. It's also known that he started a rebellion within the Soul Society and was taken down by the Royal Guard. Since then, he was sentenced to Mūken, the lowest prison level within the Soul Society and his title given to his lieutenant.

Despite being the former Eleventh Division captain, he seems to be well aristocratic, dressing and acting in such a manner. It's been also mistaken that he was from the Kuchiki Clan because of such comments on his appearence and his mannerisms, something he has a tendency to deny on most occasions and something that annoys him to no end. He has his silky black hair, finely-combed, and it's held back with a golden hair clip that keeps his hair in an upright manner. He has two long bangs hanging down neatly from each side of his face. It's said that the hair clip is a family heirloom. He wears the standard captain's haori but customized to his own standards. His collar has large golden edges with a unique designs on it. Each of his haori's sleeves is opened up a bit, revealing the black shihakushō worn underneath. He wears the standard shihakushō, but he wears a white obi tied around his waist that reaches up to his stomach.
Personality
By what's been pieced together, he was very treacherous by nature, similar to the former 5th Division captain, Sosuke Aizen. He also hated being weak or anyone that's weak for that matter. He seems to hold some form of contempt for the higher power thinking that he should be the only one in this position. When asked by the Central 46 if he released his Zanpakutō, he answered "I've just released it once." They also demanded to see it, making him angry with them. He was rebellious by nature as, considering his usurpation of the Soul Society's higher-archey through his rebellion, which was abruptly stopped by the Royal Guard. Even when he was imprisoned in Mūken, the lowest prison in the Soul Society, he was still scheming a plot. He also seemed polite and soft-spoken, as shown when when he was talking to Aizen, a man who had the same stature as he did, yet was very insulting towards him at the same time, saying that it was pathetic that he was beaten by a "strawberry-haired Shinigami."
History
Not much is known about this man's history except that he had beaten the previous Kenpachi, Kenpachi Kuruyashiki, using his Zanpakutō's Bankai. He gained this title for some form of immunity and special privileges as stated by Shunsui Kyōraku. Years later, he started a rebellion within the Soul Society. It was so dangerous that the Royal Guard was brought in to stop him. From there, he was sentenced by Central 46 to Mūken, the lowest prison within the Soul Society, where no light or sound may reach. There he spent the rest of his years until he met Sosuke Aizen, a fellow newbie of the prison. His title was given to his lieutenant and the legacy of Kenpachi continued on with him being erased from the Soul Society's history.
Abilites and Powers
Not much of his abilities is known, but it's been stated that he was the most powerful Shinigami of his time. He was so powerful that the Royal Guard had to stop him during his rebellion and he was sentenced to Mūken, the lowest prison level in the Soul Society. Also, his existence was erased in the history of the Soul Society. It's been known that he gained his title by slaying Kenpachi Kuruyashiki, the 7th Kenpachi at that time, using his Bankai, Uru Zakuro.
Master Swordsmanship Specialist: As the Captain of the Eleventh Division and the 8th Kenpachi, he's shown himself to be a powerful swordsman. He can combine it with Hakuda or Shunpō to land heavy blows on opponents, killing most in some cases. Also, it's been noted that he mastered many swordsmanship arts such as Kendō and Battōjutsu. It's been also noted that Kenpachi Zaraki or Head Captain Yamamoto are the only ones capable of engaging him in sword combat.

Kidō Master: : It's been known that he was a master at using Kidō even though he was the captain of a division that doesn't even use the art and even looked down on such skill, saying that "it's for weaklings." He's able to perform them without calling out a name, while retaining its great potential power, whereas most users require a name to do so, if not a full incantation. With the combination of his Zanpakutō's Bankai's ultimate ability, Seitai yūgō , he can imitate/copy his mouth and hands within each spaces of air, thus he is able to chant hundreds of “ittokaso” and “kurohitsugi” level kido at the same time, damaging multiple opponents.

Shunpō Master: He's noted to be very quick, even outpacing the Flash Goddess herself, yet this to yet been seen.

Hakuda|Hakuda Expert: It's also known that he was an expert in Hand-to-Hand Combat, taking out a few lieutenant-level Shin igami without getting injured in the process. This also has yet to be seen.

Master Tactician: It's been known that Azashiro was an intelligent person. He, like Aizen, tends to plot plans that'll last and can be initiated for years on end. Also, to prove his intelligence even further, it's been known that he takes about 1 year to fully understand the specs of the Soul Society and use it to dominate the Sereitei. He takes about 2 days to see through Kyōka Suigetsu and defeat it instantly, a feat only achieved by the few who knows Aizen's Zanpakutō's weakness, such as Gin Ichimaru.