Isshiki Ōtsutsuki

is a member of the Ōtsutsuki clan's main family.

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.

Appearance
Isshiki dressed in an elegant, slim cut robe with an oversized collar and extremely long sleeves, over a pair of baggy black pants tied at the ankles. The robe was embroidered with vertical columns comprised of eight magatama designs on the sleeves, and a similar pattern on the back, with the second magatama replaced with a black emblem resembling an eye. He bore some telltale features of the Ōtsutsuki clan, including a zig-zagging part in his hair and a long, curving horn, which grew from his left temple and wrapped around the back of his skull before jutting outward behind his right temple, resembling a crown.

Abilities
Isshiki's power is so vast that Jigen's body has difficulty containing it, preventing him from using the full extent of it for long. Despite his Kāma enhanced vessel being at its limit, he could still fight and pressure both Naruto and Sasuke Uchiha, the two strongest shinobi in history simultaneously, decisively defeat both of them once exerting himself, 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 shown to be a very resilient man, able to survive being bisected long enough to find a new host. Isshiki is an extremely skilled melee-combatant, both with weapons and unarmed. He has shown 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 direct kick from Naruto in his Six Paths Sage Mode. Isshiki has also displayed remarkable proficiency with a large black rod to easily parry blows from Sasuke, despite his skill in kenjutsu. Even while severely weakened from his battle with Naruto and Sasuke, he remained fully capable of matching Koji Kashin in hand-to-hand combat. While using Jigen body 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.

Isshiki wields tremendously powerful chakra, compared to Naruto in his Six Paths Sage Mode form by Kawaki. His level of chakra is so vast and powerful that his 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 if he were to be reborn in Jigen's body, the man's body would be unable to withstand it and die within a few days.

Ninjutsu
Isshiki has access to a range of techniques including manipulating the size of matter, teleportation across dimensions, chakra absorption and levitation. Utilising Yin Release, he can communicating with others using genjutsu. He can also instantly summon large black rods to impale Naruto and Sasuke, but he was even able to manifest rods directly from his body to block Sasuke's sword strike. He was also able to effortlessly absorb Sasuke's Amaterasu. Isshiki is able to produce black rods capable of draining chakra from the victim, which he can perform with the most minute of gestures such as a mere wave of his hand or even just a flick of his fingers. He appears to have his own personal dimension, a world with rolling purple storm clouds and desiccated white land, which he can use to strand his victims. The crater-shaped battlefield which he chooses to teleport foes into is actually a gigantic sealing coffin, with its lid suspended above the clouds, powerful enough to seal away even the likes of Naruto firmly by lowering and closing the lid from the sky. Only Isshiki himself is capable of breaking the seal and cracking it will only destroy whatever is inside.

Kawaki Arc
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 Uchiha. 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 Uzumaki 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.

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.