Killer B

is a shinobi from Kumogakure and the jinchūriki of the Eight-Tails.

Background
At a young age, B along with several other children were gathered in order to select a tag partner for A. Out of all the children gathered, B was the only person able to successfully perform the Double Lariat with A. As such he was given the name "B", and A stated they would be brothers from that day on. Since the age of five, B has been best friends with Motoi, whom he always greeted with a fist bump. After his cousin, the jinchūriki of the Eight-Tails lost control and killed Motoi's father along with seven other ninja on that day, B was chosen as its next jinchūriki. Soon afterwards, B suffered from similar prejudices against jinchūriki, not too different from that the villagers of Konohagakure and Sunagakure had against Naruto Uzumaki and Gaara respectively.

However, he kept smiling and pushed himself to be the best jinchūriki that he could be, so that his brother wouldn't be hurt politically as the Fourth Raikage. After his father's death, Motoi tried to kill B, believing it would also kill the Eight-Tails and avenge his father, but B disarmed him easily, and despite the attempt on his life, bore him no ill will, which led Motoi to not speak to B for thirty years out of shame. B would later train with his brother on an island in the Land of Lightning, where there he would find the Falls of Truth. There he learned how to control the Eight-Tails in the blink of an eye. Some time after his training, B, alongside A, and other Kumo shinobi confronted Minato Namikaze and his small squad. When Minato moved to counter A's attack, B used a tentacle to push A out of the way, causing shock to the Konoha shinobi that he was the Eight-Tails' jinchūriki. Some time since then, much like Naruto, B has become beloved in Kumo as the village's hero, or, as Motoi called him, the "Hero of Heroes".

Appearance
Killer B has dark-skin and possesses a muscular build, as well as white hair (blond in the anime) and a goatee. On his right shoulder, he has a tattoo of the kanji for, which is the Iron Armour Seal that was used to seal the Eight-Tails into him, and on his left cheek, he has a tattoo of a bull's horn (correspondingly, the Eight-Tails has horns like a bull, and the left one is partially missing). His top lip also has a slightly darker hue than his bottom one.

Killer B wears oval shaped sunglasses and a white coloured forehead protector. He also his village's standard one-strap-over-one-shoulder flak jacket, and a long, red rope belt tied around his waist, the standard Kumo hand and shin guards, shinobi sandals, and a white scarf around his neck. He originally carried seven swords on his back, but now only carries two swords along with Samehada.

Personality
Killer B is very proud of his own power, and like Naruto Uzumaki, has great overconfidence and can be quite cocky and stubborn, especially in terms of his own strength, demanding respect from others and asks to be called and his tailed beast be called. B has a special way of expressing his pride through song, more specifically in rap-style. He will even write his rhymes in the middle of a fight, or during an important meeting, even if they are no good. This sometimes causes the people around him to become greatly bothered by him. B doesn't respect anyone who would make fun of rap or his lyrics.

The Raikage has noted that Killer B is not the type of person to work with the strategies created by people and that he would only bring chaos into a battlefield. The Raikage also notes that he is the only being that B will listen to, as he is able to keep him in check. Despite all this, B knows talent when he sees it, and respects those with it. The primary example is his fellow Kumo jinchūriki, Yugito Nii, who he looked up to for her extreme skills. He had also praised Sasuke after their fight, stating he was one of the strongest shinobi he had ever fought. B has a very close relationship with his older brother, the Raikage. According to Motoi, the reason behind him becoming a jinchūriki was for the sake of his brother, even if it meant being shunned by the villagers. He didn't complain, and was always cheerful and determined.

Killer B seems to wish to leave his village for a vacation due to being tired of being the guardian and he can also be very lazy and not much of a hard worker, ready to transform into his full Eight-Tails form and fake his defeat and capture, only to escape from his village for a "vacation". When the Fourth Raikage, Darui and C learned that B was not captured by Akatsuki, they immediately guessed his intentions and were not surprised by it, though they were very displeased.

However, when someone close to him is in danger, Killer B has no qualms about putting himself at risk to save them, if necessary, as seen when he prioritized the safety of his singing master Sabu and his pet, Ponta, first over confronting Kisame head-on when the Akatsuki confronted his entourage. This caring nature differs him from a typical jinchūriki, most of whom are cynical and uncaring towards others. However, it was hinted that his past as a jinchūriki may not have been unlike Naruto's, since Motoi claimed that being a fellow host, B understands what Naruto went through. He has a casual relationship with the Eight-Tails, frequently engaging in friendly conversation with it, even sitting upon its nose at one time. He was also completely unaffected by Naruto's Harem Technique, resisting lustful advances and even appearing indifferent. Naruto stated that B is the first man to resist this technique. However, he is not completely unaffected by such things, as he noticed Tsunade's rather sizable cleavage, which his brother reprimanded him for.

B is also very kind and compassionate, having befriended all the giant animals on the Island Turtle which may indicate that he has a liking for animals, as well as never expressing any ill will towards Motoi who tried to take his life, nor against the villagers who used to shun him.

Abilities
As the guardian of Kumo and jinchūriki of the Eight-Tails, Killer B is an extremely powerful ninja, capable of overwhelming the entire Team Taka all by himself, and has had his skills praised by several Kumo-nin, including his older brother. Madara Uchiha claimed that he is the perfect host, a statement later reaffirmed by Kisame. Similar to how other jinchūriki obtain physical traits from their inner demon, B is able to produce ink from his mouth, which he mainly uses to write lyrics when he is lacking of regular writing tools or to blind his opponent. As expected of a jinchūriki, B has a very large reservoir of chakra, enough to make Samehada get very excited and turn against Kisame. During his time on an island where he trained to control the Eight-Tails, B tamed almost all of the island's beasts. A claimed that B had more talent than he did. B is at least knowledgeable enough of seals to know that Naruto's Four Symbols Seal is better than his own Iron Armour Seal.

Killer B has shown the ability to think on the fly, as shown when he used the Body Replacement Technique to switch places with the Eight-Tails' tentacle so he could escape Sasuke Uchiha's Amaterasu. He has also demonstrated the ability to interpret someone's "heart" as well as transmit his own feelings merely through touching someone (which is usually done through a fist bump). This ability was first demonstrated when he was training with Naruto in the Tailed Beast Temple, again when Iruka expressed his wishes to protect Naruto to him and when he stopped his brother from attacking Naruto.

Taijutsu
B possesses immense physical strength and combat prowess, capable of disarming a skilled opponent like Suigetsu with his bare hands, and winning a sumō match against a giant bear. Even as a young boy, he was the the only person to successfully perform a Double Lariat with A, allowing him to become the future Raikage's tag-team partner. He has shown incredibly fast reflexes, enough to intercept Minato Namikaze's Flying Thunder God Kunai with one of the Eight-Tails' tentacles just as he was about to stab A after using he using the Flying Thunder God Technique. His speed is great enough that when Jūgo attacked him, he was able to make it to another mountain's peak before Taka could react, requiring Karin to locate him. He is incredibly durable in battle, having received a solid kick to the neck from Sasuke Uchiha only to drop his sword and begin writing lyrics, escaping unscathed after being hit by the electricity of Sasuke's Chidori, and blasted from behind with a powerful punch from Jūgo. Killer B has a fighting style which is similar to that of the Raikage's because they both use wrestling moves instead of standard taijutsu. He supplements the speed and power of his taijutsu with his tailed beast's cloak.

Kenjutsu
While originally only carrying two swords when he was young, B has developed his swordplay to an incredible level. Possessing a unique fighting style, B holds his seven blades in between the joints of his arms (left armpit, both elbows), right leg, stomach, the right side of his neck, and in his mouth. As strange as it appears, B is very skilled with this. Because of the unpredictability of his movements, his opponents are easily overwhelmed with all of the varying swings, giving him great versatility very similar to hip-hop dance. When he finds an opening, B can impale his opponent with most of his swords quickly and simultaneously. Neither Suigetsu nor Sasuke could read his sword work, despite the former being a highly trained swordsman and the latter having the Sharingan. He is also capable of cutting through almost anything when he flows his lightning chakra through his blades. He can also use these blades as mid-range projectiles, and coat them with lightning chakra to slice right through the target. By covering himself with the Eight-Tails' chakra, he creates an "Eighth" sword.

Samehada betrays Kisame due to B's high chakra level, and B intended to use it as his main weapon, unaware that Kisame was able to hide within the monstrous blade itself, although it returned to him, after Kisame was exposed.

Nature Transformation
During the battle with Sasuke he displayed the ability to flow lightning-natured chakra through his blades to increase their cutting power, similar to Sasuke's own jutsu. Killer B's prowess in Lightning Release techniques is so great, he can charge a sharp but weak pencil-point to pierce straight through a large tree trunk and even through the ground. As stated by Kisame, B is able to do this by increasing the vibration frequency of his lightning chakra to surpass the standard penetrative force of wind chakra.

Jinchūriki Transformations
Killer B has full control over his tailed beast, something which few others have been able to accomplish. Like other jinchūriki, B has the ability to create a chakra cloak by drawing on part of his demon's power. He can then form this chakra into the form of two horns, and use them to attack the enemy with a technique called Lariat. This attack has incredible speed and power, but the linearity of his movements makes him easier to predict. Because he has a strong relationship with his own tailed beast, it acts as his partner in battle, disturbing his chakra to dispel even genjutsu from Mangekyō Sharingan.

Like his fellow Kumo-nin, Yugito Nii, B is able to become his tailed beast with great ease. Unlike her, however, he can retain complete control even in this fully released state. He can also partially transform parts of his chakra shroud into parts of the Eight-Tails' body. When fully transformed, he can easily fire a Tailed Beast Ball many times the size of its already giant body, but B was forbidden from transforming by A. B makes it a point to ignore this order when he can, either when training or to fight formidable opponents.

His control over his forms is so great, he can form all eight tentacles on his back without a cloak, and use them to balance various blocks perfectly, and form one of his arms into the Eight-Tails' arm and fist.

Invasion of Pain Arc
While leaving the Valley of Clouds and Lightning after a day of training, B is confronted by Taka. He is immediately attacked by Suigetsu, whose sword B takes and uses to overpower Jūgo. Sasuke Uchiha then steps in and uses his own sword to take back Suigetsu's. Impressed, B brings out his seven swords and assaults Sasuke, attacking him so quickly and in such an unorthodox manner that Sasuke cannot track his movements with his Sharingan. Sasuke tries to gain the upperhand by channeling lightning through his sword, so B does the same with his own swords to remove the advantage; he plunges several sword into Sasuke's chest.

Before he can finish off Sasuke, Suigetsu and Jūgo come to his defense. B is able to damage Suigetsu's sword but Taka is also able to land some strikes, including Sasuke's Chidori. B becomes bored with the fight so tries to leave, but is tracked by Karin. With escape not an option, B enters a version 1 form and attacks Taka. Taka is able to elude him and Sasuke catches him in a genjutsu, which the Eight-Tails helps B break out of. Sasuke, unaware of this, lets his guard down and creates an opening for B to hit him with a Lariat, blasting a hole in Sasuke's chest. Deciding to finish things off, B fully transforms. He fires a Tailed Beast Ball, which Suigetsu is able to protect the rest of Taka from by using himself as a shield.

Sasuke, fully healed, uses Amaterasu on B. B rampages in pain and almost crushes Karin with one of his tentacles. Sasuke severs the tentacle. B continues to writhe until he wears himself out and falls unconscious. Sasuke puts out the rest of Amaterasu's flames and delivers B to Akatsuki. While later trying to extract the Eight-Tails from this B's body, Akatsuki discovers that this is only a fake; the real B, hidden in the severed tentacle, leaves the Valley of Clouds and Lightning in secret, allowing Kumo and the Raikage to believe he was captured while he enjoys some vacation time.

Five Kage Summit Arc
B seeks out Sabu to advance his music career. In the midst of training B is found by Kisame Hoshigaki, who tracked his powerful chakra with his Samehada. While Sabu attacks him, B strikes from behind with one of his lightning-imbued swords. Not only is Kisame able to block their attacks with Samehada, but B's lightning disappears when it makes contact. B enters a version 1 form and attempts to Headbutt him, but his chakra shroud disappears too. Sabu points out that Samehada has been absorbing B's chakra.

B enters an eight-tailed version 1 form and attack Kisame again. Samehada can only absorb seven tails at a time, giving B an idea: he enters a version 2 form and creates chakra-bones to use Lariat. Kisame is badly damaged and Samehada is only able to absorb his version 2 chakra, returning B to a version 1 form. Samehada uses the chakra it absorbed from B to heal Kisame, who quickly merges with Samehada and creates a dome of water around them. B tries to get Sabu and Ponta out of the dome before they drown, but realizes that the dome moves with Kisame. He draws Kisame away from them and, once they are free, confronts Kisame, but Kisame has the advantage in water: he renders all of B's counterattacks ineffective and slowly absorbs his chakra all the while.

When B loses consciousness, Kisame dissipates the water dome. To prevent B from escaping, Kisame tries to cut off his legs with Samehada. However, Samehada has grown fond of B; in addition to not letting Kisame harm him, it transfers some of the chakra it stole back to B. Kisame kicks it away and tries to cut off B's legs with one of B's own swords, but the Raikage and his bodyguards arrive to stop him. Samehada continues to replenish B's reserves, allowing B and A to perform Double Lariat to decapitate Kisame. A then reprimands B for running away from the village.

When they returned to Kumogakure, they were greeted by the villagers at the main gate. B's students, Omoi and Karui, ask about Samehada, which he has took with him. They and B are unaware that Kisame, having faked his death, is hiding inside Samehada to gather intel on Kumo and the Shinobi Alliance during the meetings B later attends (and doesn't pay attention to).

Confining the Jinchūriki Arc
When the Fourth Shinobi World War breaks out, the Alliance decides to send the remaining jinchūriki to the Island Turtle to hide. B gets there first, allowing him to defend fellow jinchūriki Naruto Uzumaki from the Giant Squid when he arrives. Because he never got much of a vacation while away from Kumo, B tries to enjoy himself by relaxing and spending time with the island's animals. During this "vacation", Naruto approaches B and asks for help gaining control of the Nine-Tails. B senses an evil within Naruto so declines until he can deal with it. Later, when the squid attacks Motoi, B comes to his aid. Motoi apologizes for trying to kill him years earlier and B does not hesitate to make amends.

The reunion between B and Motoi shows Naruto how to overcome his inner hatred. With it vanquished, B takes him to the secret temple behind the Falls of Truth where B shows him how to enter his subconscious and confront the Nine-Tails. When Naruto first breaks the seal and releases the Nine-Tails, B tries to help him contain it. His abilities are limited while in Naruto's subconscious and he is only able to block a tailed beast ball from the Nine-Tails before being knocked out of the fight. Naruto emerges victorious and communicates all that he went through to B with a fist-bump. Naruto then demonstrates his new control of the Nine-Tails, allowing him to expose Kisame's presence.

Kisame flees with Samehada and B pursues him. Samehada tries to return to B, allowing Kisame an opportunity to absorb his chakra. When he recovers, B flings Might Guy after Kisame. Guy is able to capture him but Kisame commits suicide. They try to check the intel Kisame had with him, but it is booby-trapped and they are imprisoned while a shark swims away with the intel. B tries to catch the shark after he frees himself, but is unsuccessful. Fearing an imminent Akatsuki attack, the island's animal population is moved indoors. Because Naruto is not to know about the ongoing war, B helps keep Naruto distracted while an Akatsuki attack occurs outside.

Shinobi World War Arc
B starts helping Naruto gain control of his new Nine-Tails Chakra Mode, first by having him use his chakra arms to stack blocks in a perfect column. When Naruto masters this, they move on to transforming into the Nine-Tails. The Nine-Tails will not cooperate with Naruto on this, leaving him unable to use the Tailed Beast Ball. They instead decide to practice with Naruto's standard jutsu to see how the Nine-Tails' chakra affects them. Naruto begins with his Rasengan, which B recognizes as being based on the Tailed Beast Ball. B encourages him to focus on mastering the Rasengan in this new form.

During training, Naruto senses some of the Nine-Tails' chakra elsewhere. B tries to convince him that it's nothing, determined to keep Naruto in the training room so he doesn't find out about the war. He nevertheless lets Naruto leave to go to the bathroom. B goes looking for Naruto when he doesn't return. He instead finds Iruka Umino, who requests that B protect Naruto. Recognizing Iruka as a positive influence from fist-bumping with Naruto, B agrees. He catches up to Naruto and the two team up to break through the Thirty-Six Layer Self-Repairing Barrier to escape from the island. They then head for the battlefield.

While en route, they are intercepted by A and the Fifth Hokage. B tries to convince his brother to let them pass, promising to keep Naruto safe from Akatsuki. A is not swayed by his words and, when Naruto promises to use force to escape, A threatens to kill him. B blocks A's attack and informs his brother that he must be willing to kill both of them. A claims to have no problem with this but B, unbelieving, bumps fists with him to remind him of all they've been through together.

Trivia

 * Bī is the Japanese pronunciation of the letter "B" (as well as the Japanese pronunciation of "Bee"). This parallels the names of A, C, and J.
 * He quoted Muhammad Ali's famous line, "float like a butterfly, sting like a bee".
 * Killer B makes various references to bees. This is a pun on the number of tails his tailed beast has. Eight in Japanese is, a homophone to the Japanese word for bee,.
 * Though not confirmed, Killer B was given the name of Kira Hachi by fans. It comes from the word "Kirābī" incorrectly translated into Japanese (Hachi is the Japanese word for "bee", as well as "Eight". Kira is a loanword of the English "killer"). Kira Hachi, can be translated to "Killer Eight", following the homophone of bee.
 * The nickname of this character may be a reference to The Killer Bees, a professional wrestling team in the World Wrestling Federation. Additionally, the Double Lariat resembles the "Cross Bomber" move used by the Hell's Missionaries tag-team in Kinnikuman, a wrestling manga.

Quotes

 * "I'm the only one who gets to interrupt me!"
 * "I've got energy to spare and sparkling charm. The Eight-Tailed Beast's a killer bee rockin' the melody! OH YEAH!"