Aishia

She is your contract spirit as well as a high rank spirit, of which their existence are incredibly rare. She has been contracted with you since the start of the novel, during the time Haruto's memories awakened within your. Aishia was the one who taught you the Spirit Arts before you sets foot on Seirei no Tami after you fled from the Strahl region due to being framed for the cliff incident. Prior to her awakening in her humanoid spirit form, Aishia spent the 3 preludes arc mostly by sleeping and residing within by your side. You would occasionally hear Aishia's voice briefly in a form of inner-monologue, where she tries to help and guide you out of your predicament. Aishia would eventually manifest herself and wakes up next to you on your bed after you successfully rescued Miharu, Aki and Masato from the slave traders. Anime: Spirit Chronicle