Kinshiki Ōtsutsuki

was a member of the Ōtsutsuki clan, who served as a retainer for his foster son Momoshiki.

Background
At some point, Kinshiki consumed his guardian's chakra after they entrusted him with their power. His and Momoshiki's actions earned them Kaguya Ōtsutsuki's wariness, believing that they would one day come to steal her own chakra.

Personality
Kinshiki was very loyal and subservient to his foster son Momoshiki, to the extent that he offered himself to be changed into a chakra pill without hesitation. He also referred to his foster son using the honourific "-sama". Kinshiki also showed a vengeful side, as he was determined to kill Sasuke Uchiha for cutting his horn off from their first battle. He has no regard for anyone other than Momoshiki; this is seen when he tried to kill Sasuke as he was trying to get his daughter to safety in the middle of the chaos Momoshiki and Kinshiki brought upon their arrival to Konoha.

As a result of his extreme power, Kinshiki was very noble and self-esteemed, traits Momoshiki also came to acquire.

Appearance
Kinshiki had pale skin with short spiky blue-greyish hair, a full beard, and a long horn above his left eye that was later stubbed by Sasuke Uchiha. He had big hands and a burly physique accompanied with a towering height that reached over two metres.

He wore a pale blue shirt with back cuffs and a high collar over which he wore another darker appendage with a grey sash wrapped around his waist. He also wore grey pants and black, flat shoes on his feet which were upturned at the toes.

Abilities
Kinshiki was an extraordinarily powerful being who, alongside Momoshiki, was deemed a threat greater than Kaguya. He was capable of holding his own against multiple Kage-level opponents at the same time, and restraining a perfect jinchūriki.

Ninjutsu
Like his foster son, Kinshiki was capable of flight. He possessed the ability to absorb any kind of ninjutsu and transform the chakra into various red glowing ninja tools at will, which he was proficient with handling. He could also sense chakra, being able to locate fragments of Kaguya across countries. In the anime, Kinshiki was capable of using Space–Time Ninjutsu to transport himself to a destination.

Physical Prowess
As an Ōtsutsuki, Kinshiki possessed extremely powerful chakra. He also possessed incredible strength and durability, as he could escape being confined and immobilised by two Kage. Sasuke attributed he was strengthening his muscles with some kind of jutsu. Despite being on the verge of death, he could cut down a God Tree with a single slash of his halberd. Kinshiki was proficient in close-range combat and showed deceptive speed, being able to fight on par with Sasuke.

Byakugan
Kinshiki possessed the Byakugan, granting him a 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.

Academy Arc
After investigating Kaguya's world, Earth, he reported to Momoshiki on an unidentified planet. He stated that he had observed substantial tears and that its space curvature had exceeded 16, an abnormality that she should have reported to their clan. Wondering whether Kaguya had betrayed the clan or been destroyed by her world's inhabitants, Momoshihiki ordered him to prepare to depart.

Versus Momoshiki Arc
Kinshiki and Momoshiki encountered Sasuke, who had been travelling through another dimension to gather information on a threat greater than Kaguya. In a blizzard of another dimension, Kinshiki engaged in battle with his kanabō against Sasuke and his sword. Sasuke was nearly overpowered by Kinshiki's monstrous strength and barely escapes with his life. Later, Momoshiki used his pills to transport the pair to Earth, where they begin searching for fragments of Kaguya's chakra. There search lead them to Killer B, where they immobilised and defeated him. Afterwards, Momoshiki's absorbed his chakra, as Kinshiki reports that there is a greater source of chakra in the east, before departing there.

They appeared during the Chūnin Exams in Konohagakure and started creating chaos. Kinshiki destroyed the arena and attempted to attack Sasuke and his daughter. Shikamaru Nara uses his Shadow Sewing Technique to restrain Kinshiki and Momoshiki, but Momoshiki absorbs his power. After Momoshiki explained their goal to gather Kaguya's scattered chakra and cultivate it into a new 'cinnabar panacea' in order to gain eternal youth and supernatural powers, Kinshiki fought Naruto and Sasuke, who combined Kurama and Susanoo to shield themselves. However, Kinshiki and Momoshiki successfully captured Naruto Uzumaki when he allowed himself to be caught in their technique to protect his son, Sasuke, and Sarada.

They took Naruto to another dimension and bound him to begin the ritual of extracting Kurama from him, but the process proved to be too slow; Sasuke, Boruto, and the four other Kage arrived to rescue him. Kinshiki fought against the other Kage and was initially captured by them, but broke free from their techniques. He then unleashed a powerful blast around them, causing massive destruction and injured to himself. To everyone's horror, Momoshiki turned Kinshiki into a chakra pill and swallowed him to increase his strength.

Influence
Similar to how Kaguya was named, Kinshiki's naming convention seems to follow the Japanese folklore motif. It is a reference to Kintarō, while Momoshiki is a reference to Momotarō.

Trivia

 * Masashi Kishimoto's character sketch of Kinshiki shows him with normal-sized hands.