I think this was already posted, but maybe I saw it on youtube or another video website, don't remember.
Anyway, I think the video is a fake.
The Japanese have a thing about ghosts being trapped in mirrors and the whole horror genre is really big over there right now.
Not to mention that with the mirror the "hoaxer" has a border to work within, which makes it easier to delete the original footage and replace it with footage of the little girl still looking toward the camera.
Usually I try not to vote "real" or "fake" because there's no way to really know.
But this one has a strong scent of fake to it.