Airy initially manifests as a simple wind spirit named Aerial upon bonding with Taichi Nishimura. She belongs to a class of beings superior to humans and dragons, remaining invisible and inaudible to ordinary humans without high magical aptitude. Her connection with Taichi predates his formal summoning due to his innate magical capacity, allowing pre-awakening telepathic communication. During an early confrontation with Cassim's Red Wolf, she provisionally lends Taichi her power when cornered, though his incomplete understanding of spirit summoning magic prevents full utilization.

Following Anastasia's death, Taichi acknowledges his unique abilities and formally contracts with Airy, solidifying their pact. As Taichi's power grows, she evolves into her true form during the mid-climax battle outside the capital, revealing herself as Sylpheed—also known as Sylphy or Sylphid—Queen of Wind Spirits and one of the Four Great Spirits.

Physically, she typically appears as a palm-sized young female fairy with platinum green hair, teal eyes, and elf-like pointed ears. Her form features four feathered wings, a green hagoromo-style sash, wing-shaped hair accessories, and three diamond markings on each leg.

Her personality displays fierce loyalty, protectiveness, and profound duty toward Taichi. She expresses regret over her inability to aid him earlier, bound by strict summoning conditions. Once contracted, she demonstrates unwavering devotion, vowing never to abandon him and striving constantly to be helpful.

Her abilities are intrinsically tied to Altia's wind element, granting authority over all wind-based spells and enchantments. As Queen of Wind Spirits, her powers are formidable and fundamentally elemental.