The video is up for download at one of the good charlotte fan sites:
http://www.goodcharlottefan.net/vide.../webelieve.zip
It's terrible quality so you can't make out the faces. However, there is a Japanese at around 2 mins 23 sec. Now if only someone had a better version.
EDIT: a little better version can be found here:
http://www.hotget.com/videocode/Good...eve--3630.html
or here:
http://www.ugo.com/channels/music/vi...rticleID=15994
It's streaming but you can watch it full screen.
After watching this one, I'm not convinced that it is Ayumi, but I'm not saying it isn't either.