Keine Kamishirasawa

Keine is half human, half beast. She has the ability to conceal/erase histories, or to create them. The first two abilities belong to her human form, the last to her beast form (Ex-Keine). She's usually in her human form, so that is her "true form". She transforms into a hakutaku during the full moon, at which time all information is known to her. When the full moon disappears, she feels a little sick to her stomach. Ever a friend of the humans, she protects them from Gensokyo's many youkai. There is not one thing about the history of Gensokyo that she does not know. (Taken from Touhou Wiki)