Asuka (飛鳥あすか, "Flying Bird") was one of Kikyou's assistants; she was one of two shikigami in the form of young girls. She and Kochou primarily serve as Kikyou's messengers after Kikyou was severely injured by Naraku on Mount Hakurei.
They also act as attendants for Kikyou's other shikigami, Saint Hijiri, who is merely a puppet and vessel for Kikyou's soul. Kochou and Asuka are capable of creating and sustaining powerful barriers.
(Source: InuYasha Wiki)









