I stopped using YouTube for anything Japanese, because well... it's crap.
If you want to see Ayu's videos and EVEN MORE. Go on
www.dailymotion.com, make a search for Ayumi Hamasaki and you'll find LOTS AND LOTS of her videos, and more. I viewed a lot of small parts of her concerts, making of on there, and also some videos fan recorded when she was in Paris, signing autographes.