Kiun (黄云) is Takemikazuchi's most well-known Shinki, taking the form of a serpentine dragon made of lightning. His vessel name is Ōki (黄器).
Kiun has the appearance of a young man with long light-colored hair, some of which is tied in a knot on the back of his head. His most noticeable features are his eyes - which are drawn with dark irises and white pupils - and the horizontal scar on the bridge of his nose and another on his neck. Kiun is dressed in traditional Japanese clothing similar to the garbs worn by Shinto priests.
Kiun was summoned as Takemikazuchi's shinki at the end of the Age of Myths. Later that same day, Takemikazuchi was attacked by his other shinki and forced to reincarnate after a long battle. Because of this, Kiun had little firsthand knowledge of his original master's nature. Kiun and the 11 other surviving shinki became known as the 12 Elders, and hid the circumstances around Takemikazuchi's reincarnation. The new Takemikazuchi was forbidden from using his innate lightning powers, and instead the other elders assigned Kiun to be his guidepost and wield lightning in his place.
Over the centuries, Kiun became a shinki famous for his power, despite never achieving the status of hafuri. After witnessing both Kazuma and Yukine's power, Takemikazuchi became insistent that Kiun become a hafuri as well. Kiun was reluctant to do so, explaining that hafuri can mean either "blessing" or "burial", and related the story of a hafuri that was sealed away for betraying its master. Takemikazuchi nevertheless continued to goad Kiun into transforming, intentionally picking a fight with Yato and Yukine hoping that if Kiun was struck down by a hafuri, he would transform as well.
- Kiun's true name, 黄 ki, means the color yellow.
- The character added for Kiun's given name, 云 un, means "to say". The meaning of "cloud" has also been historically associated with it, however.
- Despite his vessel form supposedly being pure lightning, Kiun does bleed in his dragon form.
- The distinctive scar on his nose has been left by Kazuma, who interrupted Kiun's assault on Ebisu by cutting the snout and neck of his shinki form.
- Kiun is one of two currently known shinki to take the form of living creatures, the other one being Kuraha.
- Incidentally, both Kiun and Kuraha sustain damage to their shinki forms during the events of the story that leaves them scarred in their human forms as well.
- During conversation with master Takemikazuchi Kiun reveals his opinion on Blessed Regalias (originally 祝の器 hafuri no utsuwa):
«Hafuri are extremely rare. That can be seen as either a good or a bad omen. "Hafuri" also carries the meaning of "burial". One would wonder if such a thing would truly bring its master good fortune.» 
- Noragami Chapter 57 Original manga translation by fast-moon @tumblr.com