Horou

She is the first and therefore oldest conscious being, and the self-declared representative of the Old Deus. Horou is a name given to her by Sora and Shiro; She had no name prior. It comes from the word "hollow."


Until the events in volume 7 and 8, she had existed inside of Miko as conditions upon winning a game they played when Miko was a child. She doubted everything, even her own existence prior to losing to Sora and Shiro. She still asks many questions to Sora.
(Source: No Game No Life Wiki)