Often called "⑨" (pronounced "nineball"), Cirno is a childlike ice fairy which ZUN labeled in the manual of Phantasmagoria of Flower View "⑨" as a symbol of "Baka" (Stupid). Arguably, she is not very bright due to her inexperience and age. She is considered to be the strongest of her kind, but is not a difficult opponent to defeat.
So cute! It looks like she might freeze something… or someone at any moment! Thanks to Ophelia for sending this in!