Kakuzu

was a member of Akatsuki and the partner of Hidan. Despite their mutual dislike of each other, their teamwork was almost flawless, because they complemented each other's abilities extremely well. Kisame laughingly referred to Hidan and Kakuzu as the. due to the fact that in a sense, they could not die.

Background
When he was still a loyal elite ninja to Takigakure, Kakuzu took on a mission to assassinate Hashirama Senju, the First Hokage. This mission, however, ended in failure due to the might of Hashirama's Wood Release techniques. Despite the insurmountable danger faced in the mission, what awaited his return to his village was the stigma and harsh punishment associated with the failure of his objective. In response to this treatment, a wrong levied against a shinobi who had put life and limb on the line for his village, Kakuzu came to hold a violent hatred to his village as he escaped from imprisonment. In his flight from the village, Kakuzu killed the village elders, took their hearts, and fled with knowledge of the village's most prized forbidden techniques. He made a living off bounty hunting and tearing out the still-beating hearts of powerful shinobi to extend his lifespan. Some time after his defection, he joined Akatsuki, and was given a number of partners, most of whom he killed, due to his short temper. This is why he was eventually partnered with Hidan, whom he could not kill.

Sometime in the past, he appeared to have encountered the Gold and Silver Brothers, and witnessed Kinkaku's jinchūriki transformation.

Appearance
Kakuzu was a tall, dark skinned, muscular man, second in height in Akatsuki (after Kisame Hoshigaki). He wore a white hood and a black mask on his face with his eyes being the only visible part. Underneath, his mouth was stitched together at the edges, and he had long dark brown hair. His eyes have an unusual colouring: green irides, no pupils and red sclera. His clothing included the traditional Akatsuki cloak and the forehead protector of his home village with a scratch in the middle which symbolized that he was no longer loyal to it. He also had dark green nail polish and his Akatsuki ring with the kanji for was placed on his left middle finger. His entire body was covered with stitches and appeared to be sewn together. This was a result of the unique technique that he possessed - Earth Grudge Fear.

Personality
Kakuzu was a greedy, miserly individual, arranging goals in terms of the highest profit he could gain from them, and was often unwilling to involve himself in something if there was nothing to gain from it, as well as claiming that he tended to forget opponents who were not worth any money after he was done with them. He even remarked that money is the only dependable thing in the world. Due to this end, he referred to himself as the "Treasurer of Akatsuki". Given his friendly relationship with Zangei, his bounty officer, it would seem he collected bounties rather frequently to earn cash, and did so (or at least tried) during his missions on several occasions. The frequent side-tasks and devotion to money were both major points of contention between Hidan and Kakuzu. He also seemed to respect an opponent who thinks, as shown with his reaction to Kakashi's counters to Kakuzu's masks, and Shikamaru's quick analysis of Hidan's curse, even mentioning Shikamaru would have been a good bounty in the future.

Out of all the Akatsuki members, Hidan and Kakuzu displayed the most animosity towards each other, since neither of them were very fond of each other's interests. The two often traded barbs with one another, Kakuzu's usually having better timing than Hidan's. Hidan had shown great annoyance with Kakuzu's greed and occasional habit of doing or saying blasphemous things, such as attacking a temple and killing the head monk for the bounty on the monk's head. Kakuzu, in turn, disliked Hidan's religion, believing the rituals associated with it to be a waste of time. Kakuzu was also rather impatient with Hidan's drawn-out speeches and battle style.

The only reason that Kakuzu put up with Hidan was because he couldn't get rid of him. Due to his violent temper, Kakuzu often killed anyone close by when enraged. Hidan, therefore, was the perfect partner for Kakuzu, because of Hidan's inability to die. Kakuzu's somewhat indiscriminate attack style also made Hidan an ideal partner, since Kakuzu didn't need to worry about catching his partner in the crossfire.

Despite his obsessive personality and violent rages, Kakuzu was much more cautious than his partner, and was not as arrogant, never mindlessly rushing into battle like Hidan. Kakuzu frequently warned Hidan not to let his guard down, and then teased Hidan when he inevitably did. Kakuzu also seemed quite willing to follow orders. When ordered to retreat by the Akatsuki leader, Kakuzu complied immediately (while Hidan attempted to argue), despite the rather large bounty he could have received by taking Asuma. He seemed to forget the greater goals of the organisation when enraged, as he attempted to kill Naruto, in spite of Akatsuki's need to capture all the jinchūriki alive.

Abilities
Kakuzu was a very powerful ninja, as every opponent he had been seen fighting had been defeated with little effort. He had extremely high taijutsu prowess (due to his raw power and swiftness), a vast array of ninjutsu techniques consisting of multiple elements (due to his unique technique Earth Grudge Fear and near a century worth of experience) and a highly analytical mind. Those traits allowed him to fight several high-level opponents while generally controlling the pace of the fight, including Kakashi Hatake with Chōji Akimichi and Ino Yamanaka as backup.

Intelligence
Kakuzu was shown to be a keen analyst, which was somewhat attributable to his age. He is highly observant, easily noticing that Shikamaru was taking his time to formulate a plan to counter Hidan's technique, after the former caught his partner in his Shadow Imitation Technique. He was able to quickly discern the purpose of Shikamaru's various shadow attacks, and devised ways to counter them almost instantaneously during the battle. An example for that is when Shikamaru trapped him and Hidan in his Shadow Imitation Shuriken Technique, Kakuzu detached his right arm, hid it underground and with its help, was able to remove the trench knife, thus successfully breaking free from the technique.

Taijutsu
Kakuzu has demonstrated great raw speed, able to cross great distances in the blink of an eye and disappear from unfocused eyes. His raw strength was great enough to catch one of Chōji's enlarged punches with a single hand and punch down an iron gate, as well as lifting and choking two people simultaneously. This was further supplemented by his already adept taijutsu skills, shown when, during his fight with Kakashi (who was quite skilled in taijutsu himself) he mixed his hardening and extending abilities with his taijutsu. All these factors afforded him great versatility against his opponents.

Body Structure
All of Kakuzu's abilities revolved around his unique body structure, which was composed of hundreds of thick, dark grey threads woven throughout his flesh called Earth Grudge Fear, holding his body together like the stitches of a rag-doll. This allowed him to separate his body parts at will, to perform long-range physical attacks, and sew up almost any injury he suffered, making him very difficult to defeat. The threads could also be used to repair the bodies of others, as seen when he reattached Deidara's arms, although Hidan's inability to die after being dismembered caused him to be Kakuzu's most frequent patient. Because of his unique body structure, Kakuzu is a highly enduring man, able to take a direct strike from Kakashi's Lightning Cutter without it hindering his performance. His threads could even compact together to form a giant octopus-like form around his body, used for long range battle.

Kakuzu's threads granted him a degree of immortality (though he declined to think of it that way). The threads could pierce the flesh and bodies of others, allowing him to remove their organs and integrate them into his own body, thereby extending his life. He commonly removed hearts in this fashion, keeping a total of five at any time, and requiring that he be killed at least five times in a battle before he truly died.

Five Elements
The hearts captured from other ninja granted Kakuzu numerous elemental affinities, along with a vast supply of chakra. The individual hearts could be released from his body and wrapped in a vast blanket of threads, forcing a heart into a limb before being detached or forming a monstrous body with a mask as its face. These masks could move and attack independently, unleashing powerful blasts of elemental chakra from their mouths.

He could also harden other parts of his body with his mask being destroyed but not entirely.
 * Earth mask: This heart had an earth-affinity, and took on the shape of a demonic, beaked bipedal. It allowed Kakuzu to use Earth Release: Earth Spear. In the anime, even though this mask was destroyed, Kakuzu was still able to use the Earth Spear technique, though it only hardened his arm.
 * Fire mask: This heart had a fire-affinity, and took on the shape of a demonic tiger. It could use Fire Release: Intelligent Hard Work. This mask could also unite with the Wind mask to launch a fire-wind dual strike that was near unstoppable.
 * Lightning mask: This heart had a lightning-affinity, and took on the shape of some sort of deformed bipedal. It could use Lightning Release: False Darkness.
 * Wind mask: This heart had a wind-affinity, and took on a strange four-legged body with thin wings. It could use Wind Release: Pressure Damage. It could unite with the Fire mask to launch a fire-wind dual strike that was near unstoppable.

Other

 * Water: In the anime, Kakuzu could use water-based techniques. Kakuzu used the Water Encampment Wall technique when Shikamaru threw an exploding tag at him, and also a Water Clone Technique during his fight with Kakashi.

Hidan and Kakuzu Arc
Kakuzu first appeared with his partner, Hidan, in their pursuit of the Two-Tails' jinchūriki, Yugito Nii, who revealed she allowed herself to be cornered, in order to spring a trap on them and eliminate them herself. Yugito then transformed into her full demon form, a large flaming cat, but the Akatsuki duo still managed to defeat her, and gave her body to Zetsu, before they continued to the Land of Fire.

On their way, Kakuzu decided to attack the Fire Temple, in order to collect the bounty on the head monk, Chiriku, who was listed in the bingo book with a thirty million ryō bounty. They slaughtered most of the other monks during the event, but one escaped to warn Konoha of the incoming threat.

Upon receiving the notice, Tsunade assigned the Nijū Shōtai to track down and eliminate Kakuzu and Hidan. Meanwhile, Kakuzu took Chiriku's body to a bounty station hidden in a bathroom, while Hidan chose to wait outside. When Kakuzu finally left the bathroom after counting the money, he found a Nijū Shōtai team, led by Asuma Sarutobi, attacking Hidan. He attacked Shikamaru Nara in order to free Hidan, but was forbidden from further participation in the battle by the overconfident Hidan himself. Kakuzu complied, but insisted that he would get to have the thirty-five million ryō head of Asuma afterwards. In the ensuing battle, Hidan managed to ingest Asuma's blood to start his curse technique ceremony on him, but Shikamaru was able to stop him with his Shadow Imitation Technique. When Asuma managed to decapitate Hidan, Kakuzu finally intervened, and reattached Hidan's head back to his neck using the threads in his body. Kakuzu then fought with Kotetsu and Izumo, easily holding the two off, while Hidan dealt a fatal blow to Asuma. Their battle was interrupted by the appearance of another Nijū Shōtai team, but they easily fought them off, until they were summoned by the Akatsuki leader to seal the Two-Tails. Hidan and Kakuzu retreated to a secluded area, where they spent three days sealing the Two-Tails (and in the manga, another three days sealing the Three-Tails).

After the sealing was complete, Kakuzu and Hidan set out on their search for the Nine-Tailed Demon Fox's jinchūriki (Naruto Uzumaki), only to be cut off by Team 10 (with Kakashi Hatake as the leader in place of Asuma). Shikamaru used Asuma's chakra knives to capture both the Akatsuki members in place with a trick, but Kakuzu had discovered the trick beforehand, and, using a separated arm, broke free. Because of his ability to harden his skin, Kakuzu proved to be largely invulnerable to subsequent attacks. Kakashi, however, was able to analyze Kakuzu's hand seals, and pierced Kakuzu's heart with his Lightning Cutter, exploiting the weakness Kakuzu's earth-based technique had against lightning-based ones.

While this would normally be fatal, Kakuzu had five hearts (now four) in his possession, and thus recovered fairly quickly, sending a counterattack to Kakashi. Removing his cloak, he revealed four masks on his back, one of which was now broken by Kakashi. Each mask contained a heart, the broken one having given its heart up to keep Kakuzu alive. The four masks broke free from his back into separate entities, with the broken one dissolving after doing so. Each mask was able to attack with a specific and powerful elemental attack, making Kakuzu almost too much for Team 10 to handle. While Kakuzu set his sights on replacing his lost heart with Kakashi's, Shikamaru dragged Hidan away from the battlefield into some woods, with his Shadow Imitation Technique, for a one-on-one fight.

Ignoring the other two for the most part, Kakuzu focused on taking Kakashi's heart. Though Kakashi was unable to handle Kakuzu and his mask creatures, being forced to protect Ino and Chōji too, he was saved when Shikamaru tricked Hidan into using some of Kakuzu's blood in his curse ritual, which Kakashi had collected in a capsule earlier when he pierced Kakuzu's chest, and had handed it over to Shikamaru. This resulted in Hidan unintentionally destroying Kakuzu's main body's heart. Seeing this, the Lightning mask allowed its heart to be absorbed by Kakuzu's body, bringing him back to life. In addition to that, Kakuzu also had the two other Fire and Wind masks to combine with him, making him even more powerful. He then caught the rest of Team 10 with his threads, hoping to replenish his stock.

Team 10 was saved by the arrival of Team 7, among them being Naruto, who decided to fight Kakuzu himself, who at first did not view Naruto as a threat. This changed when Naruto unveiled his newly developed technique, Wind Release: Rasenshuriken, which Kakuzu recognized to be dangerous if it ever connected with him. Naruto's inability to maintain the technique for more than a few seconds put Kakuzu at ease, especially since its failure almost allowed him to kill Naruto (although Yamato and Kakashi saved him), but decided to fight in his long-range mode just to be safe. As Naruto tried the Rasenshuriken once again with his shadow clones, Kakuzu attempted to crush Naruto with his threads from a distance, but was surprised to discover that it was a shadow clone that he had destroyed, and, subsequently, the real Naruto shot up behind him, using the technique effectively this time.

Left with no usable hearts after being battered by Naruto's technique, Kakuzu lamented being defeated by those he considered "kids". Kakashi assured him that the previous generation being surpassed by the next was perfectly natural, and one of the "never-ending cycles of life". Kakashi then finished him off with a Lightning Cutter.

Kakuzu's corpse was later taken back to Konoha to be autopsied by Tsunade in regards of the Rasenshuriken's capabilities, and it revealed that Kakuzu was damaged at a cellular level by it.

Confining the Jinchūriki Arc
Later, he is resurrected by Kabuto, along with Itachi, Nagato, Deidara and Sasori, through the Summoning: Impure World Resurrection, as a demonstration of power to Madara.

Shinobi World War Arc
When given the order to set out, he moved in the same direction as Itachi, whilst carrying Nagato on his back since the latter can no longer walk. Kakuzu soon emerged from the water along with several thousand of the White Zetsu Army and other powerful ninja such as Dan, Asuma Sarutobi, and Hizashi Hyūga in order to battle the First Division. While Kakuzu strangles multiple shinobi with his threads, he glanced over to see Kinkaku's transformation, noting he had not seen it in a long time.

Kakuzu quickly confronted the members of the new Ino-Shika-Chō, concluding that if Shikamaru's still alive, he probably decapitated Hidan to defeat him; but the fact that Hidan isn't among the resurrected is the proof he's still alive. Kakuzu reaps the last and fifth heart from a shinobi and proceeds to free his masks to help his comrades. Also, Kakuzu told them that if even though they have captured the Gold and Silver Brothers, they have "more pieces" on their side, pointing at Dan and Asuma. Before he made any other movement, Kakuzu's arms are cut by Izumo Kamizuki and Kotetsu Hagane while wrapping him with chains. While he managed to escape from his captors, who both give chase, his lightning release heart is accidentally destroyed by Asuma Sarutobi's Wind Release: Dust Cloud Technique. Also, while he continues to fight Darui, Izumo, and Kotetsu, he was surprised to see Chōji's butterfly wings overshadowing the battlefield. Later he is seen immobilized underneath Chōji's giant fist. During the Demonic Statue of the Outer Path's rampage, when Chōji leaves to face the statue, he tells them that they will have to deal with Kakuzu. He is later seen being sealed by a shinobi.

Trivia

 * Although covered by his hood, Kakuzu had shoulder length dark brown hair, but in the anime it was depicted reaching down to his lower back.
 * When Kakuzu first appeared as a hologram at the end of Part I, he was clearly the tallest Akatsuki member there, a fact reinforced when he appeared during Gaara's sealing ritual. However, when he truly appeared with Hidan, he was much shorter, and the 3rd databook stated that he was shorter than Kisame.
 * The first kanji in Kakuzu's name (角) stands for kakugyō, the bishop in shogi. While similarly, the kanji in his parter Hidan's name means "rook", another shogi piece.
 * Kakuzu's unusually coloured eyes were similar to those of Hanzō.
 * Both Hidan and Kakuzu's faces appeared on a pair of lanterns in the omake of Shippūden episode 129, Kakuzu being on the right and Hidan on the left.
 * At some point after the 'Kazekage Rescue Arc', he reattached Deidara's arms.
 * Kakuzu, along with Hidan, gets a mention in Naruto Shippūden: Dragon Blade Chronicles for the Wii, when Tobi mentions "monsters" with traits of the two (arms that can be stretched and the ability to survive decapitation), before Deidara notes how he is talking about the pair's abilities.
 * According to the databook:
 * Kakuzu's favourite food was liver while his least was kurikinton (sweet potato mixed with cooked chestnuts).
 * He wished to fight anyone with a high bounty.
 * His hobby was reading old books.
 * He was short tempered and greedy.

Quotes

 * (To Hidan) "Make sure he's recognizable when you're finished with him."
 * (To Hidan) "Even Hell runs on money. I'd be just fine."
 * (To Kakashi) "Looking at your forehead protector reminds me of the very first Konoha shinobi I fought … the First Hokage, that is."
 * (To Hidan) "Start training your mind instead of your body, Hidan."
 * (To Shikamaru) "You actually think… unlike my partner."
 * (To Hidan) "Keep talking, and I will kill you."
 * (To Hidan) "Hidan, anyone with a brain would know that the world revolves around money!"
 * (To Kakashi) "Heh… No one is immortal."
 * (To Kakashi) "It's only fitting that I take your heart to replace the one you've destroyed!"