Killer B

is one of the major supporting characters in the series, a shinobi from Kumogakure and the jinchūriki of Gyūki, 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 A's cousin, the jinchūriki of Gyūki 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 Gyūki 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 Gyūki in a amazingly short period of time. 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 Gyūki's jinchūriki. From this encounter Minato would come to have much respect for B and his abilities. 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".

When A became the Raikage, he forbade B from fully transforming into the Eight-Tails and restricted him from leaving the village, saying instead that he would become the guardian of the village and attack from within its walls.

Personality
Killer B is very proud of his own power and also very proud of who he is. Like Naruto Uzumaki, who has great overconfidence, Killer B 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 and tends to use when referring or speaking to others. He will even write his rhymes in the middle of a fight, or during an important meeting, even if they are no good, which is usually the case. This sometimes causes the people around him to become greatly annoyed 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; in his youth he was already seen completing missions, that were supposed to be assigned for both him and his brother, without A's knowledge. 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.

Due to the fact that he was confined to the village very soon after his brother assumed office and made the village's guardian, B desperately wished for a vacation and was even ready to fake his capture for one. 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. This lead to him receiving his brother's "Iron Claw" as punishment. B also tends to fist bump with others. This ties into his rapper personality and also serves as a means of communication of sorts, with others without the need to speak.

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 prioritised the safety of his singing master Sabu and his pet, Ponta over confronting Kisame head-on when the Akatsuki confronted his entourage. This caring nature differentiates him from a typical jinchūriki, most of whom are cynical and uncaring towards others due to their circumstances. However, it was hinted that his past as a jinchūriki may not have been unlike Naruto's, since Motoi claimed that being a fellow jinchūriki, B understands what Naruto went through. He has a casual relationship with Gyūki, frequently engaging in friendly conversation with it, even sitting upon its nose when not in combat. He was also completely unaffected by Naruto's Harem Technique, resisting lustful advances and even appearing indifferent. However, he is not completely unaffected by such things, as he noticed Tsunade's chest, which his brother reprimanded him for and he later stared at Yugito's own chest when it was shown during his fight with Tobi's Six Paths. This is later explained as having a preference toward older woman, at one point confessing it during the fight against Tobi, much to his tailed beast's surprise and chagrin.

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.

Appearance
Killer B has dark skin and 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 Gyūki into him, and on his left cheek, he has a tattoo of a bull's horn (correspondingly, the Gyūki 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 has 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 he only carries two swords on his back and stores the rest inside Samehada.

As a child, B's hair was much shaggier and he wore a simple suit along with his trademark sunglasses and scarf along with Kumo-nin shin-guards. In his adolescent years, his hair grew much longer and he wore it in a stylised, combed-back manner. In these years he donned the standard uniform of the Kumo-nin inclusive of shirt and started carrying two Supervibrato Lightning Release Swords. As he got older, he started wearing his forehead protector like a bandanna.

Abilities
As the guardian of Kumo and a fully-realized jinchūriki, Killer B is an extremely powerful ninja, capable of overwhelming the entire team Taka single-handedly, and has had his skills praised by several Kumo-nin, including his older brother. Even as a child, B showed promising skill, being able to accomplish missions all on his own, despite the fact that they should have been executed as a team, with A as his partner. Tobi claimed that he is the perfect jinchūriki, a statement later reaffirmed by Kisame. Even Minato Namikaze praised B's abilities, stating that he was more like a ninja with a great power than simply a jinchūriki. During his time on an island where he trained to control Gyūki's power, B tamed almost all of the island's beasts. A claimed that B had more talent than he did, which was shown when he overpowered his elder brother in a direct Lariat clash. Using Gyūki's power, despite a past injury, he was able to hold his own against two tailed beasts while fighting alongside Naruto in his Tailed Beast Mode.

Despite his seemingly carefree nature, Killer B possesses sharp wit, as shown when he used the Body Replacement Technique to switch places with Gyūki's tentacle so he could escape Sasuke Uchiha's Amaterasu. He also has 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.

B is also quite knowledgeable in fūinjutsu, able to distinguish between the superiority of the Four Symbols Seal to his own Iron Armour Seal as well as possessing a unique style of fūinjutsu.

Taijutsu
B has immense physical strength and combat prowess, capable of easily fending off all three male members of Taka at once, despite all three being dangerous fighters, while still holding back, as well as 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. During the Fourth Shinobi World War, it was seen that B's Lariat is stronger than that of his brother's, not even needing Gyūki's chakra to overpower him despite A being clad in his lightning armour.

He has shown incredibly fast reflexes, enough to intercept Minato Namikaze's kunai with one of Gyūki's tentacles, as well as being able to quickly react to Sasuke Uchiha attacking him at close range and block and repel him with a single move. B is also immensely fast as when Jūgo attacked him from behind, B was able to instantly dodge his attack and make it to another mountain before Taka even saw he was gone, requiring Karin to locate him.

B is also 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. He could take one of A's Lariats straight to the chest with no visible damage. 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. B can force his opponents on the defensive with his style and when he finds an opening, B can impale his opponent with most of his swords quickly and simultaneously.

Neither Suigetsu Hōzuki nor Sasuke Uchiha, both highly trained swordsmen with the latter also being a Sharingan master, could read his swordplay. He is capable of cutting through almost anything when he flows his lightning chakra through his blades. B can also use these blades as mid-range projectiles. By covering himself with Gyūki's chakra, he creates an "Eighth" sword. Even with just two blades, B is highly proficient in his sword skills, able to quickly finely slice rocks into various shapes. After obtaining Samehada, B intended to use it as his main weapon. He has integrated Samehada into his fighting style by taking advantage of the sword's ability to 'cut' chakra, allowing him to bisect Itachi's Fire Release: Great Fireball Technique. Samehada and B are capable of working in tandem; while it attacks the enemy on its own, B attacks them from a blind spot. B also uses Samehada to store five of his swords while keeping the other two on hand.

Nature Transformation
Killer B has displayed the ability to flow lightning-natured chakra through his blades to increase their cutting power. 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 high enough to surpass the standard penetrative force of Wind Release techniques.

Jinchūriki Transformations
As a jinchūriki, B has a very large and strong levels of chakra, enough to make Samehada get very excited and betray Kisame. Killer B is one of the few people to have achieved full control over a tailed beast as noted by Danzō Shimura, achieving this control with ease at the Falls of Truth, greatly surprising the spectators. Like his fellow Kumo-nin, Yugito Nii, B is able to transform into his tailed beast with great ease, reaching a full transformation in mere seconds and is able to maintain control even in this fully released state. B is the only known, as well as living jinchūriki who can at will, transform and remain in his full tailed-beast form indefinitely. 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 the Mangekyō Sharingan. This makes B's "control" over Gyūki more of a willing partnership than actual dominance. Despite his undeniable control, B was forbidden from transforming by A. B, however, disregards this, either when training or fighting formidable opponents.

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. The pinnacle of his jinchūriki prowess is his ability to easily fire a Tailed Beast Ball. He can fire one many times his own size or even multiple ones. While in full Eight-Tails form, B can spin to summon up a great force of wind that can destroy an entire forest with ease. He has shown immense durability using Gyūki's power, able withstand Amaterasu long enough to make an Octopus Leg Clone, Kokuō's Horn Breaking, despite being sent crashing a considerable distance, Son Gokū's Lava Release, and Saiken's Leech Gap, as well as being able to survive his own Tailed Beast Ball. The beast has lost several of its tentacles throughout the series which it has been able to regenerate. This ability, however, does not seem to extend to its horns; one of which was cut off by A.

B's skill with partial transformations is such that he can form all eight tentacles on his back without a cloak and do so very quickly, allowing him to intercept fast opponents, or have them burrow through the ground and catch an opponent off guard. His dexterity with these tentacles is able to stack and balance various blocks perfectly. B can transform one of his arms into that of Gyūki's to use for various purposes such as throwing fellow ninja a long distance away or blocking attacks. Similar to how other jinchūriki obtain physical traits from their inner beast, 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. This ink can be used in a more solid form to make ink clones which immobilise his enemies through wrestling locks. After the opponent is captured, the clones proceed to trap and seal them.

Invasion of Pain Arc
While leaving the Valley of Clouds and Lightning after training, B was confronted by Taka. He was immediately attacked by Suigetsu, whose sword B took and used to overpower Jūgo. Sasuke Uchiha then stepped in and used his own sword to take back Suigetsu's. Impressed, B brought out his seven swords and attacked Sasuke, his unorthodox fighting style preventing Sasuke from tracking his movements with his Sharingan. Sasuke tried to gain the upper hand by channelling lightning through his sword, but B did the same with one of his swords, removing the advantage, and plunged the other six into Sasuke's torso, dealing him a critical wound.

Before he could finish off Sasuke, Suigetsu and Jūgo came to his defence while Karin retreated with Sasuke and healed him. B was able to damage Suigetsu's sword but Taka was also able to force him back. Sasuke was healed by Karin and the fight continued. B became bored with the fight and tried to leave, but was tracked by Karin. With escape not an option, B entered his Version 1 form and attacked Taka. Taka was able to elude him and Sasuke caught him in a genjutsu, which Gyūki helped B break out of, allowing B to hit the unaware Sasuke with a Lariat, blasting a hole in Sasuke's chest, again mortally wounding him. Deciding to finish things off, B fully transformed into his tailed beast. He then fired a Tailed Beast Ball, which Suigetsu was able to protect the rest of Taka from by using himself as a shield.

Sasuke, specially healed by Jūgo, used Amaterasu on B. B rampaged in pain and almost crushed Karin with one of his tentacles. Sasuke severed the tentacle, and B used the opportunity to escape and fake his capture, by substituting with the severed tentacle and leaving behind a decoy. Taka were unaware of this, and delivered "B" to Akatsuki while the real B left the village to go on vacation. While later trying to extract Gyūki from this B's body, Akatsuki discovered that this was a fake.

Five Kage Summit Arc
Free from his confinement to Kumogakure, B sought out Sabu to advance his music career. In the midst of training B was found by Kisame Hoshigaki, who tracked his powerful chakra with his Samehada. While Sabu attacked him, B struck from behind with one of his lightning-imbued swords. Not only was Kisame able to block their attacks with Samehada, but B's lightning disappeared when it makes contact. B entered a Version 1 form and attempts to Headbutt him, but his chakra shroud disappeared too. Sabu realised that Samehada was absorbing B's chakra.

B entered an seven-tailed Version 1 form and attacked Kisame again but Samehada absorbs most of his chakra. Upon realising that Samehada could only absorb six tails at a time, B entered a Version 2 form and created chakra-bones to use in a more powerful Lariat. Kisame was badly damaged and Samehada was only able to absorb his Version 2 chakra, returning B to a Version 1 form. Samehada used the chakra it absorbed from B to heal Kisame, who quickly merged with Samehada and created a dome of water around them. B tried to get Sabu and Ponta out of the dome before they drown, but the water dome moved with Kisame. B drew Kisame away from Sabu and Ponta, in order to force him to release them to pursue B. Once they were free, B confronted Kisame, only for Kisame to render all of B's counterattacks ineffective and slowly absorb his chakra all the while.

When B lost consciousness, Kisame dissipated the water dome. To prevent B from escaping, Kisame tried to cut off his legs with Samehada. However, Samehada had grown fond of B's tailed beast chakra during the battle and betrayed Kisame; in addition to not letting Kisame harm B, it transfered some of the chakra it stole back to him. Kisame kicked it away and tried to cut off B's legs with one of B's own swords, but the Raikage and his bodyguards arrived to stop him, having noticed Kisame's water dome. Samehada continued to replenish B's reserves, allowing B and A to perform Double Lariat to decapitate Kisame. A then reprimanded B for running away from the village.

When they returned to Kumogakure, B now carrying Samehada, they were greeted by the villagers at the main gate. B's students, Omoi and Karui, ask about Samehada. They and B were unaware that Kisame, having faked his death, was hiding inside Samehada to gather intel on Kumo and the Shinobi Alliance during the meetings B later attended (and didn't pay attention to).

Confining the Jinchūriki Arc
Shortly before the Fourth Shinobi World War began, the Alliance decided to send the remaining jinchūriki to Kumogakure's Island Turtle to hide. B arrived there first, allowing him to defend fellow jinchūriki Naruto Uzumaki from the island's Giant Squid when he arrived. Shortly after this, Naruto approached B for help gaining control of the Nine-Tails. B refused, having noticed an evil within Naruto, and also due to Naruto accidentally insulting his rap. Later, when the squid attacked Motoi, B came to his aid. After the squid was subdued, Motoi asked B why he saved him, despite surely knowing about Motoi's earlier attempt on his life. B's reaction was to act like it had never happened, and did not hesitate to reconcile with Motoi.

After observing the reunion between B and Motoi, Naruto was able to overcome his inner hatred. With it vanquished, B took him to the secret temple behind the Falls of Truth, to allow him to battle the Nine Tails for control of its chakra. When Naruto first opened the seal and released the Nine-Tails, B tried to help him contain it. His abilities were limited while in Naruto's subconscious and he was only able to block a tailed beast ball from the Nine-Tails before being knocked out of the fight. Naruto eventually emerged victorious and communicated all that he went through to B with a fist-bump. Naruto then demonstrated his new control of the Nine-Tails, allowing him to expose Kisame's presence.

Kisame fled with Samehada and B pursued him. Samehada tried to return to B, allowing Kisame an opportunity to absorb his chakra. When he recovered, B flung Might Guy after Kisame. Guy was able to capture him but Kisame committed suicide to prevent the group from interrogating him. They tried to check the intel Kisame had with him, only to be imprisoned while a shark swam away with the intel. B tried to catch the shark after he freed himself, but was unsuccessful. Fearing an imminent Akatsuki attack, the island's animal population was moved indoors. Because Naruto was not to know about the ongoing war, B helped keep Naruto distracted while the other members of the group fought the Akatsuki outside.

Shinobi World War Arc
To keep Naruto occupied, B started helping him 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 mastered this, they moved on to transforming into the Nine-Tails. The Nine-Tails would not cooperate with Naruto on this, leaving him unable to use the Tailed Beast Ball. They instead decided to practice with Naruto's standard techniques to see how the Nine-Tails' chakra affected them. Naruto began with his Rasengan, which B recognised as being based on the Tailed Beast Ball. B encouraged him to focus on mastering the Rasengan in this new form.

During training, Naruto sensed some of the Nine-Tails' chakra elsewhere. B tried to convince him that it was nothing, determined to keep Naruto in the training room so he wouldn't find out about the war. He nevertheless let Naruto leave to go to the bathroom, unaware that it was a lie from Naruto. When Naruto didn't return, B went looking for him, but instead found Iruka Umino, Naruto having found out about the war, and headed off to try and stop it. Iruka requested that B protect Naruto, and after recognising Iruka as a positive influence from fist-bumping with Naruto, B agreed, and went after Naruto. When the Eight Tails protested, B reminded him that they were still training, and stated that real world experience would always be faster than training. He caught up to Naruto and the two teamed up to break through the Thirty-Six Layer Self-Repairing Barrier to escape from the island. They then headed for the battlefield.

While en route, they were intercepted by A and the Fifth Hokage. B stated he thought Tsunade was attractive. B tried to convince his brother to let them pass, promising to keep Naruto safe from Akatsuki. A was not convinced by his words and, when Naruto promised to use force to escape, the Raikage threatened to kill him. B blocks the latter's attack and informed his brother that he must be willing to kill both of them. A claimed to have no problem with this but B, unbelieving, bumped fists with him to remind him of all they had been through together. B further stated that since A became the Raikage, he has failed to see B's development in strength, and has therefore underestimated him. Still unconvinced, both he and Naruto tried to combat him but struggle doing so as A manages to fight them off. B and A later simultaneously hit each other with their respective Lariats, with B overpowering his brother.

B explained how he overpowered A with his Lariat; his true strength, along with Naruto's, came from the people that believed in them, not just the beasts inside of them. A eventually pushed B out of the way and activated his Lightning Release Armour again, seemingly intending to kill Naruto. Naruto dodged A, who revealed that he attacked in order to test Naruto. Impressed, he and the Hokage let them pass.

B and Naruto later encountered several shinobi, including F who told B that they were to return to headquarters as back-up. Before he could continue however, Naruto attacked him revealing that he and the other shinobi were transformed enemies much to B's shock. After taking out a few of the clones, B watched on with amazement and pride as Naruto took out the enemy, while noting that in response to Naruto's Tailed Beast Chakra mode the Zetsu were turning into trees in the same manner Yamato's wood creations did at the Tailed Beast Temple. Later while Naruto arrived just in time to save two shinobi from Toroi's onslaught, he had a conversation with one of his fellow Kumo-nin before setting out once again.

While en route with Naruto, the two encountered Itachi Uchiha and Nagato. As the battle commenced suddenly with Itachi being forced to use the Fire Release: Great Fireball Technique, B used Samehada to slice through the attack effectively saving both him and Naruto, although Samehada was unhappy about being used to cut through hot flames. As Itachi appeared behind B suddenly and used the Fire Release: Phoenix Sage Flower Nail Crimson technique, B countered with his transformed arm. B then used the tentacle to grab Itachi, only for him to disappear in a flurry of crows. As Itachi told B not to look into his eyes, Gyūki broke B out of the genjutsu he had already been caught in. He then charged Itachi using his seven swords. Itachi retreated onto Nagato's summoned bird.

As Itachi activates his Mangekyō Sharingan B tried to stop him by throwing his sword but it was repelled by Nagato. As a result of his Sharingan use, Itachi activated a crow he had stored in Naruto earlier, which was able to free him from Kabuto's control. Itachi, now on Naruto and B's side explained to Naruto and B why the crow had a Mangekyō Sharingan and how he got it. Nagato, after recovering from Itachi's attack and being completely controlled by Kabuto, sneaked behind them with his chameleon summon and used Shinra Tensei to attack Killer B and Naruto. Nagato appeared behind B and tried to attack him, but B went into his Version 2 transformation and countered Nagato's attack with a Lariat. Nagato used the Preta Path's ability to absorb B's chakra, causing him to regain a youthful appearance.

Seeing Naruto in dire straits with his soul being removed, B moved to attack Nagato. Nagato, sharing vision with his own chameleon summon and the King of Hell, intercepted B by using his Asura Path abilities. Before Nagato could fatally injure B and remove Naruto's soul, they were rescued by Itachi's Susanoo. As Nagato used Chibaku Tensei in an effort to trap them, Itachi told them to attack the centre of the sphere in an attempt to dispel the technique. With the combined force of B's Tailed Beast Ball, Itachi's Yasaka Magatama and Naruto's Wind Release: Rasenshuriken, the sphere was dispelled. B watched on as Itachi's Sword of Totsuka began to seal Nagato who passes on his final words to Naruto, before passing onto the afterlife.

After Itachi claims that he will stop the Summoning: Impure World Reincarnation technique, B voiced his doubts and recalled that they were not able to kill the reincarnated ninja, just seal them. Itachi reminded them again that no matter how infallible a technique may seem, it always had a weak point. As Naruto stated that he would end the war and attempted to create shadow clones he reverted to his normal self, having used up too much of the Nine Tails's chakra. After Itachi told Naruto not to try to shoulder everything himself, B told him that he had made a promise to Iruka to protect him.

B was later scolded by Gyūki for taking too long to urinate and for letting Naruto go ahead of them. When Naruto's clone contacts them mentally, wanting help for fighting the reincarnated Third Raikage, he asked B to let him speak to Gyūki to which B refused while urinating. However, the clone still got to speak to the beast because it could overhear mentally. After catching up to him, B and Naruto ran into Tobi with his Six Paths of Pain.

After a short skirmish with the other jinchūriki, and conversing with Gyūki about the jinchūriki and Yugito's fate, B enquired about the "other Madara" that Naruto was speaking of. Looking on smiling as Naruto told Tobi that it wasn't all bad living with a tailed beast inside them, he declared that he would go first before staring in shock as the other jinchūriki began their tailed beast transformations.

Shocked that they still had their tailed beast skills, B attacked Fū head-on nonetheless. After she dodged several of his and Samehada's attacks, Naruto informed him of the shared field of vision that the Six Paths of Pain possessed using the Rinnegan. Catching Naruto, B fled the vicinity after seeing Yugito unleash her Mouse Hairball technique. Clashing with her while escaping, he was able to land a somewhat shallow attack on her that immediately begins repairing. This opportunity however, allowed B to see where Tobi had implanted the chakra receivers in his Six Paths. After Naruto's attempt to destroy the receivers in Rōshi's chest was thwarted, B agreed with Gyūki that the forest was too much of a hindrance for them and transformed into Gyūki to level the entire forest.

B immediately moved to seal the revived jinchūriki with his Octopus Hold technique but it was unsuccessful as Tobi caused the jinchūriki to enter Version 2-like states. As they began counter-attacking, B and Naruto tried to fend them off, but began feeling the pressures of fighting six powerful opponents. B was attacked by a fully transformed Han, who gored him with his horns and sent him flying, seemingly knocking him unconscious. After B came to, he asked Gyūki if it was all right to which it replied that they were both wounded. After Tobi lost total control over the Five-Tails and restrained it with a chakra chain, B attempted to crush him within Gyūki's fist, but Tobi simply slipped trough it.

As the Five-Tails was being subdued, B and the Eight-Tails asked Naruto if he had also heard Five-Tails' voice and the Eight-Tails then lamented that seeing other tailed beasts treated that way naturally annoyed the rest of them. While Gyūki and the Nine-Tails were talking telepathically, Naruto suggested using shadow clones to create a diversion and allow them to strike Tobi, B urged Naruto not to as he would die due to the Nine-Tails sucking away his chakra. However, Gyūki revealed that the Nine-Tails had seemingly stopped doing this for some time now due to Naruto's stable condition after using so much of the beasts' chakra. He then got tossed away by a fully transformed Rōshi. B was later impressed when Naruto managed to escape Son Gokū's stomach using shadow clones.

After Naruto successfully removed the chakra receiver, B watched on with shock as the beast was resealed into the Demonic Statue of the Outer Path in the blink of an eye. As Naruto rallies, telling the beast and B to get ready, it told him that he and B would be take the front-line while Naruto acted as support because he was still unable to transform into the Nine-Tails. After Naruto told them it would be fine because they were a pair of duos, he wondered whether Kurama had finally come around. As the battle began, to B's astonishment, Naruto assumed the form of his tailed beast before joining the fray.

During Naruto's attack, Gyūki stopped the Three-Tails from attacking him, and also repelled another attack from the Five-Tails. After the Three-Tails freed itself from Gyūki's tentacles, they watched on as the five beasts prepared a collaborative Tailed Beast Ball and Naruto prepared to negate the attack with one of his own. As Gyūki wondered if Naruto would be able to do it, B told it that he almost did it during his training, but was sure that Naruto would be able to do it now.

As the two Tailed Beast Balls collided, B grabbed Rōshi's body and protects himself from the after-effects of the attack as he noted that Naruto hit the base of the other attack allowing it fly into the air. He later congratulated Naruto on freeing the other beasts, before advancing behind Naruto, Guy and Kakashi prepared to fight Tobi directly. Later, as Naruto mocked Tobi with the information he had just learned, B looked on smirking. After the jinchūriki's corpses are enveloped in a light of sorts as the Impure World Reincarnation technique is released, B told Naruto that they had to pick up the pace to compete with Itachi's contribution. He is later seen mobilised beside Naruto, Kakashi and Guy as they prepare to assault Tobi and the Demonic Statue of the Outer Path.

While the shinobi regroup and discuss the gash in Tobi's mask. B uses the opportunity to attack the statue. Moving in with a punch, he declared that the statue was wide open. However, his attack was deflected by Tobi's Uchiha Flame Battle Encampment barrier which burned his hand. Telling Naruto that he was okay, B prepared to launch the strategy that Kakashi had developed. Holding all the shinobi in his hands, B threw the trio towards Tobi. When they regroup after Tobi's arm is hit by a seemingly unseen attack, B listened to Kakashi's explanation of Tobi's technique and then enquired if all Space–Time Ninjutsu shared the same dimension. When told no, B told Naruto that it still would not be easy to land an attack on an intangible person. When Kakashi stated that their belief that Tobi was becoming intangible was incorrect, B enquired once again how it was possible for their two Sharingan to share the same dimension. As the battle against Tobi continued Tobi shot multiple stakes at Gyūki and B which are made to bind and suppress a tailed beasts power using his Space–Time Ninjutsu. Incapable of assisting because of the stakes, B is left to observe as Naruto successively breaks Tobi's mask revealing his true identity as Obito Uchiha. When the real Madara arrived to the battlefield, B asked Naruto what this could mean for the Kage, distressed at the possibility of something happening to his brother. When Madara casually disregarded the situation, Naruto used his tails to free him of the stakes, and threw them at the Uchiha, however, Madara easily blocked the stakes with a barrier. Madara then told Obito to handle Kakashi and Might Guy, while he dealt with B and Naruto.

As the battle with Madara ensued, B was seemingly knocked to the ground, leading the beast to comment on Madara's power. When an injured Guy told them that was why Madara was worth fighting, the beast told Guy that he shouldn't be pushing himself so hard. As the battle waged on, he and Guy were restrained by Madara, before the Uchiha can land the finishing blow, he is intercepted by Naruto. After Might Guy's Daytime Tiger sends the legendary ninja flying away from them, B noted that Guy wasn't just acting tough. After breaking free of his constraints, B warned Naruto that the wood could suppress a tailed beast's power before turning his attention to the statue. Forming a collaborative tailed beast ball with Naruto, B fires it at the statue and believed it to be destroyed. Their celebration, however, was cut short when the smoke cleared and the Ten-Tails appeared on the battlefield.

Asking Kurama if it really wanted to fight that, Gyūki is told that it could not hide from the beast. Handing over Guy as per the fox's request, the two beast were attacked by the Ten-Tails surprising them with its speed. Ending up on either side of the beast, B signals to Gyūki to fire the Continuous Tailed Beast Balls at the beast. When the smoke cleared, Gyūki was nowhere to be seen. It was later revealed, as B announced their strategy, that Kakashi had warped them right above the Ten-Tails to launch a Tailed Beast Ball at point-blank range. The Ten-Tails flicks his Tailed Beast Ball back at him. With B's full transformation now having reached its limit, Gyūki tells B to buy him some time while he generates more chakra to use. As the Ten-Tails fires a Tailed Beast Ball, the attack is misdirected by the timely arrival of the the entire Allied Shinobi Forces.

With the Alliance having bought enough time, B flew towards the Ten-Tails on the back of one of Sai's birds with his chakra now replenished. As the beast prepared to launch a Tailed Beast Ball towards the shinobi, B transformed into the Eight-Tails and prepared a Tailed Beast Ball of his own. Recklessly stuffing Gyūki's head into the beast's mouth, B was able to stop the attack as well as harm the Ten-Tails as both Tailed Beast Balls detonated inside it. Casting aside Omoi's words of caution, he noted that when it came to protecting everyone he was fearless.

Creation and Conception
Masashi Kishimoto in a 2012 Shōnen Jump interview, stated that one of his past editors who really likes pro wrestling greatly influenced his decision to create a character that — even though he was a shinobi — used pro wrestling moves as part of his techniques. He also stated that he wanted to make him into an interesting character and one of the most powerful shinobi in the series. Kishimoto went on to say that he has trouble writing B's lines at times because he always wants them to rhyme due to his rapping style.

Trivia

 * His name is a reference to the famed rap group, the Wu-Tang Clan, often referred to as the "Killer Bees".
 * Though it is unconfirmed, in his flashbacks in the manga, Killer B was only ever referred to as B until his confrontation with Minato, where B is praised as a "killer shinobi". Since then B has been known as Killer B, suggesting that it was Minato who bestowed him the title "Killer".
 * Bī is the Japanese pronunciation of the letter "B" (as well as the Japanese pronunciation of "Bee"). This parallels the names of other Kumogakure shinobi such as F and J for example.
 * During a fierce battle with Taka, B 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.
 * B's nickname 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.
 * B has used or has possession of two of the Seven Swordsmen of the Mist blades so far. He used Zabuza Momochi's Kubikiribōchō in his fight with Taka and he has taken possession of Kisame Hoshigaki's Samehada.
 * In chapter 542, when A and B face off against several Iwagakure shinobi while on a mission, B is first depicted with longer hair and looks a bit older. However, in subsequent panels his hair is once again short and spiky and looks much younger. Oddly, this was not corrected in the tankōbon.
 * In a 2012 Shōnen Jump interview, Masashi Kishimoto stated that Chōji Akimichi and B were currently his favourite characters in the Naruto series.

Quotes

 * (To Suigetsu) "I'm the only one who gets to interrupt me!"
 * (To Jūgo) "I've got energy to spare and sparkling charm. The Eight-Tailed Beast's a killer bee rockin' the melody! OH YEAH!"
 * (To Sasuke)
 * (To A) "Becoming a jinchūriki, you can lose a lot, and your heart goes hollow, but if you got things you don't want to lose, they become a light to follow! The tailed beasts aren't our only source of strength! What was inside our hearts before the monster... shines like a sun, powers us to any length! That's where our true power comes from!"
 * (To A) "Brother, I'm a big idiot as you said too, and Naruto is as well, right dude? But the ones who accomplish things are the big idiots that don't care about how thick and strong the wall is, yahoo."