Isshiki Ōtsutsuki

is a member of the Ōtsutsuki clan's main family, the former partner to Kaguya, and the true leader of Kara.

Background
Coming to Earth alongside Kaguya with the objective to plant a God Tree to harvest its Chakra Fruit, Kaguya turned on Isshiki before it was eaten, and in the process Isshiki's lower half was destroyed, resulting in him being on the verge of death. Encountering Jigen and not having the strength to implant a Kāma on him, Isshiki devised a desperate plan and shrunk himself to enter the monk's ear in order to survive his injury by absorbing Jigen's nutrients. Through time, Isshiki came to control Jigen's entire body and embed a Kāma onto his host. Passing on reviving himself through Jigen as his body would probably die within a few days as it wouldn't be able to bear his chakra, he instead began preparing for a new host.

Upon the formation of Kara, Isshiki through Jigen became its leader, and the Inners collectively agreed on obtaining the Chakra fruit by cultivating a new God Tree huge enough to devour all life on Earth. Eventually, Isshiki found and purchased Kawaki from his abusive father with a large sum of money, to use as a potential new vessel. After taking custody of the boy, Isshiki introduced Jigen as his new father and reassured him. With the assistance of Amado, who at some point modified Isshiki's vessel with Scientific Ninja Tools, the two attempted to transfer Kāma to Kawaki and fourteen other boys in an experiment, with Kawaki being the only known success and survivor. Despite promising him safety, Isshiki put Kawaki through gruelling training to master the Kāma and would constantly berate him as only having value as a vessel, striking the boy whenever he questioned him.

Personality
Isshiki is arrogant, pragmatic, and ruthless. Having crushed Jigen's mind and completely taken over his brain and body, Isshiki is unconcerned with the damage his overwhelming power inflicts on Jigen's body, mocking his tears of pain and declaring him to be a worthless and defective vessel, and he is also shown to be able to enjoy battles and outright mock enemies, as he repeatedly insults Naruto and Sasuke upon overpowering them decisively and relishes in their expressions of awe and fear of his power, even going as far as to say he enjoyed the battle and thanking them for the fun. Despite his ruthlessness and arrogance, Isshiki is shown to be able to remain calm even when faced with insults, ignoring Naruto's mockeries and sealing him instead of killing him as he doesn't want to expend the chakra needed to kill Naruto due to Kurama. He desires Kawaki, who has been groomed as his next vessel, and is interested in Boruto Uzumaki, who bears Momoshiki's Kāma.

Generally, Isshiki appears to be formal and courteous, addressing the fellow members of his organisation politely before beginning their meeting, and even extends his manners to his enemies, as he politely greeted Naruto Uzumaki, and apologised for not removing his shoes when entering the Uzumaki household. He also lacks the confrontational tendencies of Delta, preferring to only incapacitate enemies when not necessarily having to kill them and even willing to avoid conflict if potential adversaries are agreeable to his terms, as shown by how he merely left Naruto pinned down after he easily knocked him aside and was willing to accept Kawaki's deal of sparing Naruto if he returned willingly. He does have a serious and authoritarian side to himself, as he is fully capable of commanding respect among the group, to the point even prideful Victor and hot-tempered Delta are easily silenced by him. He is very composed and systematic in his approach to matters at hand. Even when dealing with momentary failure, he remains determined as ever, convinced that all will fall into place as he designed it.

Although he may prefer to avoid battles, when he has to fight he is shown to be very confident in his abilities, bordering on arrogance. When facing Naruto and Sasuke, the well-considered two strongest shinobi in history, he was completely unfazed at the prospect of facing them. At the same time, this self-confidence doesn't prevent Isshiki from praising his opponents and also remaining calm when cornered, commending Sasuke Uchiha for his intellect and mastery of his dōjutsu along with actually thanking them for revealing the weakness of his absorption abilities instead of lashing out. At the same time, he has shown an irritable side, as when tasks fail to reach his expectations, he can lash out, as he kicked a broken tank after another setback to his plans. He is also shown to be a perfectionist, viewing his work on Kawaki and his Kāma as work of great importance and expressing disgust to see his adopted son's preference of his prosthetic right arm over the left arm that held the seal and quickly expressing his desire to restore his right arm.

He is also shown to have a very amoral and remorseless side, caring not in the slightest at how many innocent lives he must sacrifice to obtain his goals. His single-minded nature views all his actions towards Kawaki, no matter how harsh, as truly in his best interest. Apparently, he views those who value peace as the utmost priority as being cowardly and foolish, likewise considering Naruto a peace-obsessed idiotic coward who only cares for the peace of his village, and considers Kawaki's attachment to Konoha as being a weakness, openly degrading the village in an attempt to convince his adopted son to distrust Konoha and leave with him willingly. Arrogant as he appears, Isshiki is very cautious and secretive, capable of keeping the full scope of his abilities secret even from his allies. He's very perceptive and deceptive, as he was fully aware of Koji Kashin and Amado's treason, yet still hid it fully from the other Inners, feigning complete trust to the point of admonishing Delta for not following Koji's way of executing the mission of retrieving Kawaki and likewise reassuring Amado he would be rewarded for his service, and was able to easily trick Koji into revealing his desire to know Isshiki's secrets and ultimately make him and Amado expose themselves.

Isshiki is so driven in his goals that he is noted to get over-excited and reckless in battle from the idea of things proceeding so swiftly. As long as it obtain results, Isshiki appears fully willing to solve problems with a great amount of financial investment, as Delta noted that money Isshiki had invested for his experiments, where the final result was Kawaki being turned into the "vessel," was enough to buy an entire country. His immense devotion to his goal is such that he shows no interest to other serious matters such as Naruto, who he did not even bother to finish off upon defeating, but became interested in Boruto for also bearing Kāma, believing the boy would be like Kawaki, a "perfect Ōtsutsuki" that will further Kara's plan and having intended to take him back along with Kawaki to Kara.

Isshiki seems to believe that all living beings have their fates predestined by their genetics, as he stated that Koji, a clone of Jiraiya, is destined to die just like his template due to having inherited his genes.

Appearance
Isshiki bore the telltale features of the Ōtsutsuki clan, including a long, curving horn which grew from his left brow and wrapped around the back of his skull before jutting outward from his right temple, resembling a crown. The iris and pupil of his right eye had a wheel-like pattern with eight spokes coming out of the centre, while his left eye was a Byakugan. He bore matching tattoos on his chest and back: on his chest was a vertical column of six magatama topped with an emblem resembling a black mallet across his chest, and on his back was a vertical column of six smaller black mallet emblems. His hair, right eyebrow, and goatee were trimmed short with unusual alternating zigzag patterns resembling the hair parts worn by other members of his clan, while his nails were painted black.

Isshiki prefered to dress in an elegant, slim cut, long-sleeved tailcoat with an oversized collar that folded back upon itself, over a pair of baggy black pants tied at the ankles. The coat was embroidered with patterns matching his tattoos, with vertical columns comprised of eight magatama designs on the sleeves, and a similar pattern on the back, with the second magatama replaced with the black mallet emblem.

Abilities
Isshiki's power is so vast that Jigen's body, despite the various enhancements he gained to be monstrously powerful in his own right, has difficulty containing it, preventing him from using the full extent of it for long. While limiting himself, he could pressure both Naruto and Sasuke Uchiha, the two strongest shinobi in history simultaneously, and upon exerting himself more, decisively defeat both of them, sealing the former while nearly killing the latter. Amado described Isshiki's power as being so immense that if he were to be able to fully harness his true powers, he could destroy Earth with no one able to stop him.

Isshiki also has considerable senses, as he was easily able to sense the presence of Koji's toad that went unnoticed even to Naruto. Isshiki also can seemingly manifest items as he sees fit, replacing destroyed furnishings and chemical reactions, such as a table, food and drink, and even lit candles.

Physical and Chakra Prowess
Isshiki is a very resilient man, able to survive being bisected long enough to find a new host. While possessing Jigen, Isshiki displayed incredible prowess unarmed combat. Even without having Jigen's body access more of his power, he shows tremendous speed and strength, easily kicking Naruto away, impressing the Hokage with his reaction, and effortlessly catching a punch from Kawaki when he had Kāma activated, causing Kawaki visible pain by merely lightly twisting his arm. He is also highly durable, suffering no injuries from a direct kick from Naruto in his Six Paths Sage Mode. Even while severely weakened from his battle with Naruto and Sasuke, he remained fully capable of matching Koji Kashin in hand-to-hand combat. Isshiki has also displayed remarkable proficiency with a large black rod to easily parry blows from Sasuke masterful skill in kenjutsu.

Isshiki wields tremendously powerful chakra, compared to Naruto in his Six Paths Sage Mode form by Kawaki. Its sheer reserves and strength at full power is capable of overwhelming Jigen's body with the sheer intensity of it. Even while limiting himself, his sinister chakra was already strong enough to terrify Ino Yamanaka to the point of near-collapse. When unleashing more of his power through Jigen's Kāma, his chakra was such that it intimidated Sasuke into fleeing and later on unnerved both him and Naruto. As noted by Amado, his chakra is so massive that it requires a proper vessel to withstand it, as if he were to be reborn in Jigen's body, the man's body would die within a few days.

Ninjutsu
Isshiki has access to a range of techniques including manipulating the size of matter. He can use chakra absorption powerful enough to absorb Sasuke's Amaterasu, and levitation. Utilising Yin Release, he can communicate with others using genjutsu. He can also instantly summon large black rods to impale his foes to wield as a melee weapon, to which he shows adept bojutsu prowess. Isshiki rods are also capable of draining chakra from the victim, which he can perform with the most minute of hand gestures. He can use Space–Time Ninjutsu, able to connect between two targets bearing his mark and accessing what appears to be personal dimension, a world with rolling purple storm clouds and desiccated white land. The crater-shaped battlefield is also a gigantic sealing coffin, with its lid suspended above the clouds. He can also use the lid to perform a power Fūinjutsu, able to seal away even the likes of Naruto inside. Only Isshiki himself is capable of breaking the seal and cracking it will only destroy whatever is inside.

Kāma
As an Ōtsutsuki, Isshiki impart a Kāma onto individuals. This seal, being a compressed backup file of Isshiki's biological data, grants the host his powers and techniques, including a huge boost in physical and chakra levels, as well as to absorb chakra. While using vessel with its enhanced Kāma, Isshiki displays such a tremendous level of physical strength and speed that he was able to effortlessly dodge Sasuke's Complete Body Susanoo and Naruto's Tailed Beast Mode attacks and plunge them out with a single attack as well as pummel them severely with just a few punches and kicks. He is also resilient enough to be completely unfazed by being burned by Amaterasu, which could harm even Tailed Beasts, proceeding to calmly absorb it.

The true purpose of Kāma is for Isshiki's genetic information to overwrite that of the host, allowing him to transcend death and be reborn at the expense of the vessel's individuality. Isshiki applied the Kāma onto Jigen after nearly dying against Kaguya's, but knowing Jigen's body would die days later resurrecting through him, Isshiki used the Kāma instead to better control Jigen's body as a vessel. Nevertheless, Jigen's would endure great damage if accessing too much of Isshiki's power for prolonged periods of time.

Through scientific aid, Isshiki was able to transfer his Kāma to a more suitable vessel, albeit with a very low success rate, with Kawaki alone out of fifteen children to have survived the process. At the same time, Isshiki would still have to mature Kawaki seal enough through arduous training to make the resurrection work properly. Isshiki is also able to synchronise the Kāma he placed onto Jigen with that on Kawaki to open rifts in space between the two vessels.

As with any Kāma, Isshiki had no control over its progress once it is applied. Hence, when he and Jigen were burned to death by Koji, Isshiki was forced to reincarnate into an incomplete state using Jigen's charred corpse. At the moment of reincarnation, every other Kāma that Isshiki placed vanished, thus preventing Isshiki from stockpiling on backup vessels for further reincarnation, leaving him vulnerable to a permanent death unless he could apply another Kāma.

Byakugan
As an Ōtsutsuki, Isshiki possesses a Byakugan, though he seemingly cannot access it when in a vessel and only in his true form. It presumably grants him the usual near 360° field of x-ray vision (with the presumed exception of a small blind spot at the upper thoracic vertebrae) and the ability to see the chakra pathway system.

Ao Arc
Upon an aircraft carrying Kawaki crash landing, Isshiki held a meeting with the other Inners of Kara to discuss the urgent situation, during which Koji was given the task of recovering Kawaki. As he dispelled the genjutsu, Isshiki voiced that their group must recover the vessel at all costs.

Kawaki Arc
While eating a meal with Delta, she voiced her frustrations about the time it was taking to recover Kawaki, during which Isshiki gave her permission to partake in the recovery of the vessel with the condition that she follow Koji's ways. Later, after Delta's decisive defeat by the Seventh Hokage, upon Isshiki silencing the argument between her and the other Inners and asking on what Koji was doing, she reported that Koji was holding off on retrieving Kawaki to study Boruto after learning that the boy obtained his own Kāma. Smirking at this development, Jigen deduced that Momoshiki was behind this. Later, he transported himself to the dimension containing a Ten-Tails, and began speaking nonchalantly to it. Failing to eat his vessel, Isshiki comments on it being too soon as needed to complete his vessel, before absorbing its chakra using his Kāma. Afterwards, Isshiki intended to visit Boruto and Kawaki.

While attempting to capture Kawaki from Naruto Uzumaki's household, Jigen transported Naruto to another dimension with the intent of abandoning him there to die, but was attacked by Sasuke. During the ensuing battle Jigen was driven back and resorted to unleashing the full power of his Kāma, manifesting Isshiki's personality. As he quickly overpowered Naruto and Sasuke, pummelling them into submission, Jigen's body began to break down, which frustrated Isshiki as he disabled Naruto and Sasuke with giant black rods and reaffirmed his dire need to possess Kawaki. Revealing the crater acting as their battlefield was actually a gigantic coffin, Isshiki intended to kill Sasuke as he could escape any time and seal Naruto and Kurama within it, as he couldn't exert the power needed to kill Naruto due to Jigen being weakened. Sasuke escaped with Naruto's help and Isshiki brushed off Naruto's insults and revealed he was never interested in him as Kurama noted and that he was after Boruto for his Kāma, promising to kill Naruto if he escaped as Isshiki successfully sealed Naruto within the coffin, which he shrank to a normal size. Before teleporting away, Isshiki cursed Jigen's weakness as a vessel.

Having returned to Kara's headquarters, Isshiki had Amado treat Jigen's body, with the scientist informing him that it would take two days to fully recover. Excited as the progression of Kawaki's Kāma, he believed that it was due to exposure from Boruto's own mark. From this, Jigen strongly believed the two of them would become "perfect" Ōtsutsuki and form a God Tree to consume the planet. He also assured Amado that everyone would get what was promised. Later, while he had only returned to ten percent of his power, he received a report from Code who he had sent to guard the Ten-Tails. Afterwards, he was approached by Koji whom he asked for a report from. Informing Kawaki wasn't recovered, Koji questioned why he was tasked with the mission when Isshiki could have teleported to his location. Justifying his actions, Isshiki accused Koji and Amado of crashing the airship carrying Kawaki to allow him to escape.

Questioning his motives, Koji attacked Jigen, leading to the two fighting and Isshiki being informed Koji wanted to kill him. As Isshiki continued to repel Koji's various assaults, he voiced that the latter was nothing but a tool, having committed himself so fully to one goal. As Koji continued his attack while Isshiki fully unleashed his Kāma, he eventually caught Jigen off-guard, summoning a giant wall of flames. As Jigen failed to absorb them, Koji explained that he summoned naturally occurring flames void of chakra, meaning the mark was powerless before it as the flames began to consume him.

Jigen tried to shrink the flames, but he could not maintain it for long due to his body reaching its limits. As Jigen's body was killed, and Kawaki's Kāma had yet to fully decompress, Isshiki was forced to fully reincarnate using Jigen as an imperfect vessel. He instantly shrunk and dispersed flames around him. Isshiki began shrinking various targets around him, forcing Koji to dodge. Ultimately, Isshiki's assault destroyed Koji's mask, revealing him as a clone of Jiraiya created by Amado.

Trivia

 * Like other male members of the Ōtsutsuki clan, Isshiki was named after a Japanese folk hero whose name includes "Tarō", in this case Issun Kotarō, a hero from Japanese folklore who was only an inch tall, popularly known as Issun-bōshi. As a boy he went on an adventure to rescue a girl from an ogre, triumphing after being swallowed by it and using his sword — a needle — to attack it from within. He then claimed the ogre's magic hammer, Uchide no kozuchi, and used it to transform into a full-sized adult.

Quotes

 * (To Koji Kashin) "All genes… all people have a predestined fate. That man bore a mighty fate… a star of change. Now I understand. Amado had wanted to cling to it, to that man's mighty fate, to the minuscule possibility of change… Koji Kashin, clone of Jiraiya of the Sannin. That you shall die here, was also predestined by your genes!"