Asuka (飛鳥あすか, "Flying Bird") was one of Kikyou's assistants; she was one of two shikigami in the form of a young girls. She and Kochou are mainly used as Kikyou's messengers after Kikyou was grievously wounded on Mount Hakurei by Naraku.

They are also attendants for Kikyou's other shikigami, Saint Hijiri, who is just a puppet and container for Kikyou's soul. Kochou and Asuka are also capable of erecting and maintaining powerful barriers.

(Source: InuYasha Wiki)