Aishia is a high-ranking humanoid spirit contracted to the protagonist, Rio, in Seirei Gensouki. Her existence is exceptionally rare, and she has been connected to Rio since the awakening of his past life memories. For a long time, she resided within him, communicating through brief inner monologues or dreams to offer guidance. She first physically manifests after Rio rescues Miharu, Aki, and Masato from slave traders. Aishia possesses an otherworldly, divine beauty with extremely long peach-colored hair reaching her knees and gem-like eyes of the same shade, though her expression is almost always flat and emotionless, and she speaks in a monotone. Despite her reserved exterior, she is deeply caring and curious about human experiences such as eating good food, taking baths, and wearing cute dresses. Her entire existence is dedicated to Rio, whom she often calls by his past life name, Haruto; all her actions are ultimately for his benefit, though she will advise against or even disobey orders if she believes Rio would suffer unnecessarily. As his primary combat partner and teacher, she instructed him in Spirit Arts and fights in perfect synchronization with him, able to trace his martial arts and use all elemental attributes at their strongest level. She possesses powerful telepathy, capable of communicating across vast distances, and can disrupt magic from divine weapons with anti-magic spirit arts. Her bond with Rio is central, and she also shares deep connections with Ayase Miharu and Celia Claire, often acting as an intermediary in Rio’s relationships. Later revelations tie her origins to a divine goddess, with her soul sharing a connection to Miharu. Aishia is held in high reverence by the spirit-folk, who address her with the honorific -sama, and even powerful spirits like Dryas acknowledge her formidable strength.