Aira is a silver-haired girl encountered by protagonist Ran amidst a battle between the Hazard revolutionary group and the Rodoist religious cult. Her origins are intrinsically linked to the Holy Mother, the central Rodo monolith revered by the Rodoists as the sole source of water and life on a post-apocalyptic desert Earth.

Seized by Hazard leader Kiba for interrogation due to her significance to the Holy Mother, Aira is later captured by Rodoist forces during an attack and transported to Green 5, the settlement surrounding the monolith. There, the actions of the five unpleasant Rodoist bishops trigger her latent abilities, leading the Holy Mother to identify her as the crucial missing twelfth silver-haired maiden required to complete a set.

The Holy Mother intends to use Aira and the other maidens to restore Earth's green environment through a terraforming operation that would simultaneously transform humanity into plant life. Aira voices strong protest against this plan. During the terraforming process, her emotional response to hearing Ran call her name disrupts the harmony of the twelve maidens. This interruption causes the Holy Mother's plan to fail, resulting in a partially transformed Earth where only some humans become plants.