Ah-Un is the two-headed dragon yokai that travels with Sesshomaru and often protects Rin when she is left alone. Ah-Un is sort of hard to describe, but I’d say he’s covered in brown scales with a body sort of like an ox with two horse-like necks and heads. As far as I know, he’s the only herbivorous yokai in the series and is non-aggressive except in the course protecting Rin. Both of those traits I find interesting since he’s a dragon yokai, and I’d think they would eat meat and be violent. Ah well. Ah-Un does not communicate verbally, but is obviously intelligent and has an individual personality in the same way as Kirara.

Very little is known about Ah-Un, his origins, or when he became part of Sesshomaru’s retinue. His primary role seems to have been that of a pack animal. Despite having been with Sesshomaru for what may have been centuries, no one bothered to ever give him a name until Rin came along. When traveling long distances, Rin and Jaken usually ride on Ah-Un’s back.Despite not speaking and being used as a beast of burden, Rin treats Ah-Un as a friend and equal. Ah-Un seems to be very fond of Rin and is protective of her, always taking her side in the many disagreements with Jaken. Ah-Un has saved Rin on a multiple occasions. The two most memorable examples are when he her from some lesser yokai while she is collecting herbs to save Jaken when he is poisoned by Naraku’s miasma and when he protected her from the zombie warriors in the third Inuyasha movie, Swords of an Honorable Ruler.

Ah-Un can project yokai energy from both of his mouths. From the right head, which is Ah, he fires beams of blue lightning. His left head, Un, fires green lightening which allow him to control clouds and probably the weather. However, he's never used his green lightening to directly attack anything and it’s possible that it isn’t harmful.