Asia first appeared in Volume 1 as an underling of Raynare, which in reality was a plan by the latter to steal Asia’s Sacred Gear. After having her Sacred Gear removed from her body which resulted in her death, Rias revives her as a Devil under her as her Bishop. She moves into the Hyoudou Residence after Issei rescues her from the Fallen Angels and transfers to Kuoh Academy, where she is in the same class as Issei.
As befitting a nun, Asia is extremely shy, innocent and fairly inexperienced in things like socializing. Despite being reincarnated as a Devil, Asia still believes in God and follows His teachings such as praying to Him and reading the Bible, which would usually result in her getting severe headaches.
Asia has the Sacred Gear Twilight Healing, which allows her to heal humans, Devils, Angels, and Fallen Angels alike. Asia herself shows no actual fighting technique, and mostly relies on her healing abilities. She can send the healing powers of Twilight Healing in a form of a projectile, but it is slightly inferior to her direct touch.
Asia has been blessed by Ophis, granting her a bond with Dragons, and allowing her to make a pact with Fafnir. This pact allows her to summon him, with the price being a pair of her panties each time.