Isshiki Ōtsutsuki

is a member of the Ōtsutsuki clan's main family, currently using Jigen as his vessel.

Background
While much of Isshiki's history is unknown, he seemingly originally came to Earth alongside Kaguya Ōtsutsuki but they split up. Later, at an unknown period, his Kāma was passed to Jigen, who became his vessel. Some time after, he gave Kawaki his Kāma and began cultivating him into a suitable vessel for him.

Personality
Isshiki is arrogant, pragmatic, and ruthless. Though it is unclear exactly where Jigen's personality ends and Isshiki's begins, 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, limiting the extent to which he can wield it. Despite his Kāma enhanced vessel being at its limit, he was still capable of simultaneously defeating the strongest shinobi in history.

Ninjutsu
While unknown who truly wields these techniques, Isshiki has access to a range of techniques including manipulating the size of matter, teleportation across dimensions, chakra absorption, and levitation.

Kawaki Arc
While attempting to capture Kawaki from Naruto Uzumaki's household, Jigen transports Naruto to another dimension with the intent of abandoning him there to die, but is attacked by Sasuke Uchiha. During the ensuing battle Jigen is driven back and resorts to unleashing the full power of his Kāma, seemingly allowing Isshiki's personality to manifest. After quickly disabling Naruto and Sasuke, he reveals that the crater acting as their battlefield is actually a gigantic coffin, and that he plans to kill Sasuke and seal Naruto and Kurama within it, as his current vessel is too weak to kill Naruto. He reaffirms his need to acquire Kawaki to use as a vessel, and expresses interest in Boruto Uzumaki's Kāma. Sasuke manages to escape with Naruto's help, but Isshiki successfully seals Naruto within the coffin, which he then shrinks to a normal size. Before teleporting away, Isshiki curses 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.