Where are you seeing Japan as #1 in volume? Looking at
http://data.bitcoinity.org I'm seeing these volumes for the past couple weeks:
| Volume (in BTC) | Week 7/23 | Week 7/16 |
| USD/BTC | 621k | 982k |
| CNY/BTC | 180k | 255k |
| JPY/BTC | 94k | 168k |
Looks like Japan's volume is still way behind both China and the US.