Sakura, the Princess of Clow Kingdom, lost her powers and her memories because of a powerful force, causing her to be weak and confused. Her memories take the form of feathers scattered in different dimensions which she and Syaoran must collect in order to return Sakura back to normal.
Another beautiful cosplayer from Comiket! Unfortunately, we can't see her face clearly, but the photography is still superb. Wonderful job to both the cosplayer and the photographer!
EDIT: Thanks to the cosplayer, Kashino Rei, for contacting me! Apparently, this is not from Comiket, but rather in Hanami, an event in Germany! You may view the original image in her Deviant Art account!