Ao

is a shinobi of Kirigakure and skilled enough to be a member of his country's ANBU Hunter-nin squad.

Background
Ao is an experienced veteran, having been raised under the feared regime of the Bloody Mist and having fought in war, even before the advent of the Fourth Shinobi World War. He has clashed several times with Konoha shinobi. At one point he defeated an unknown Hyūga, taking one of the Hyūga's Byakugan and implanting it into his own right eye socket. Later, he had a confrontation with Shisui Uchiha, which left enough of an impact on Ao for him to clearly remember Shisui's abilities and his chakra color long after the event.

Appearance
Ao is a middle aged man with a patch over his right eye, under which he hides a Byakugan he took from a Hyūga clan member he defeated. He wears a talisman in each ear with the kanji for written on them twice on each side. These talismans react when his Byakugan is under threat and will protect it from anyone, even himself. He also wears a striped shirt and pants with seemingly the same pattern, with a green robe over them. His blue hair bears a resemblance to that of Kisame Hoshigaki, while his attire is strikingly similar to that of Haku.

With the outbreak of the Fourth Shinobi World War he has taken to wearing the standard outfit of the shinobi alliance with a Kirigakure Flak Jacket over.

Personality
Ao has shown to be prideful and somewhat masculine as he believes that men should be tough and decisive, constantly scolding Chōjūrō for his pessimistic and weak demeanor. This attitude seems to be caused by his up-bringing during the times when Kirigakure was known as the Bloody Mist Village. He has a tendency of bringing up how things were done during those days, usually while fussing over Chōjūrō's behavior.

Abilities
As a member of Hidden Mist's hunter-nin, Ao is a highly capable tracker and has extensive knowledge of the human body. He is also a highly skilled sensor shinobi. With his sensory skills he could even pick out the resurrected shinobi out of thousands White Zetsu.

Byakugan
At some point in the past Ao had a Byakugan from a defeated member of the Hyūga clan transplanted into his right eye. His skill with it is notable, as he said that his eye saw through the illusion placed on the Fourth Mizukage. With it he was able to detect that Danzō had the right arm and eye of Shisui Uchiha transplanted into his body, and immediately recognized the chakra color emanating from those areas. It is also notable that unlike a transplanted Sharingan, the Byakugan can be activated at will, rather than being in a constant release stage. The Byakugan is protected by the talisman seals that Ao wears as earrings, and will cover the eye if anyone tries to take it. The seal cannot be deactivated by anyone (not even the Mizukage) except the hunter-nin of Kirigakure.

Five Kage Summit Arc
He was setting off with Chōjūrō to escort the Fifth Mizukage to the Five Kage meeting, called for by the Fourth Raikage. There he scolds Chōjūrō for his indecisiveness.

After traveling for some time, the small group stopped at an inn to eat and rest. After being told that the Fourth Mizukage's teachings are to be forgotten, by both the Fifth Mizukage and Chōjūrō, he yells at the latter for not being able to make up his mind as to what to order for dinner and sends him to get food.

After arriving at the summit in the Land of Iron, Ao sits behind the Kiri curtain listening as the Kage have their meeting. When the Fourth Raikage crushes the table in a fit of anger, Ao, along with the other attendants, move to protect their respective Kage. The commotion ends and the attendants return to their seats. Later while the Kage are discussing the possibility of making Danzō the head of the alliance, Ao notices his chakra with his Byakugan; he then points out that Danzō confiscated his Sharingan and arm from Shisui Uchiha, someone he'd fought in the past. Before he can prove the accusation, Zetsu appears and Ao moves to defend the Mizukage. After the Raikage seemingly kills white Zetsu, he tells Ao to watch Danzō. When Danzō states that he cannot use the mind controlling jutsu that many times in one day, Ao says that he is unsure if he's lying and that he can no longer trust Danzō. When Fū and Torune try to go and battle Sasuke, Ao tells them to stay right there as the Raikage told him to watch over them and when they get into battle position Danzō tells them to stop. He later demands that Danzō and Fū stop whispering, revealing that he's also a sensor and knows that they have been located.

When Sasuke finally reaches the meeting room, Ao is the first to notice his presence. When Sasuke is attacked, Ao and Karin simultaneously notice that Danzō is attempting to escape. Ao asks permission to follow, and is told not to follow him too far. He begins his pursuit after telling the Mizukage he would leave the Akatsuki (Sasuke and his comrades) to her. Sasuke attempts to follow with Karin in tow, but is promptly stopped by the Mizukage. On his way, Ao is also trapped by Zetsu's Spore Technique, but he manages to get free from it; only to be suddenly trapped by Fū's Mind Puppet Switch Cursed Seal Technique. Fū, following Danzōs orders, tries to cut out Ao's eye. However, Ao tells Fū that there is a special seal in his eyes, making it impossible for enemies to try to take his eye. As Fū decided to improvise by making Ao decapitate himself, Ao warned Fū to time it carefully as too soon would allow Ao to dodge and too late would take Fū down as well.

Before the true outcome could happen, the Mizukage and Chōjūrō arrive and save Ao. Fū, still in control of Ao, tried to trick the Mizukage into removing the seal on his eye, but she saw through Fū's deception when he acted kindly to Chōjūrō's insult. The Mizukage then punches Ao in the face for calling her an old hag, unaware that Fū already ended the jutsu.

Confining the Jinchūriki Arc
Ao later escorted Mei to a meeting of the leaders of the Allied Shinobi Forces. He was also seen at the alliance's headquarters making preparations along with the other shinobi.

Shinobi World War Arc
He was appointed captain of the Sensor Division of the Allied Shinobi Forces. Ao and Inoichi Yamanaka were later seen working together to create a Boundary Barrier.

He later states the fact that if it had not been for Muta Aburame's information they would have had no idea that the enemy were traveling underground. He then tells his division members to shift the barrier downwards to pick up on the enemy's exact location. Upon hearing of the large amount of enemy forces heading towards the First Division, Ao uses his sensory abilities to hone in on the revived shinobi on the battlefield while the others maintaining the barrier focused on the large scale sensing. Ao discovered that they were many resurrected shinobi amongst the troop all of which were infamously strong during their lifetimes. He then reports that there are two persons on the battlefield with immense chakra reserves tinged with the chakra of the Nine-Tailed Demon Fox. They were later identified as Kumogakure's Gold and Silver Brothers.

Trivia

 * means "blue" or "green".
 * There seems to be a running gag of when Ao scolds Chōjūrō, Mei always mishears it as something offensive towards her love life, such as "arrangements" for "engagements", and "call you ambitious" for "called off", and threatens to kill Ao if he doesn't shut up, much to his confusion.
 * Ao killed a member of the Hyūga clan to obtain his Byakugan eye, but it is unknown whether he killed a Main or Branch House member. It is however likely that he killed a member of the Main House or he removed the eye of a Branch member while his opponent was still alive; whether the Hyūga seal prevents this is unknown.