ナノ

A mysterious creature that only communicates with Adele. It watches over the nanomachines that make up people's magic in the other world. In the manga, it appears as a tiny, sphere-bodied robot, while in the anime it looks like a young cat. Nano's character is a personification of the nanomachines featured in the novel series, where their manifestations are far more impersonal.

(Source: Wikipedia)