The last time I was there, I did not see much graffiti in Japan. The first piece of graffiti that I did see was in Shinjuku, Tokyo by non-other than New York graffiti artist Cope2.
Cope2 in Shinjuku, Tokyo Japan
Apparently, there are lots of great graffiti in Japan. The pictures below are courtesy of Remo Camerota who wrote the upcoming book Graffiti Japan. Check out his website: GraffitiJapan.com. I will also review the book once it becomes available.
Graffiti in Japan
Graffiti in Japan - Belx2
Graffiti in Japan - RDWriter
Barry McGee exhibit at the Watarium gallery in Aoyama
Shizento Motel in Kanagawa
More Graffiti in Japan