Statistics shows that the trading volume in dollars and yen higher than ever, but some believe that these figures should be taken in excess. For example, when China dominated the bitcoin market, this is due to the fact that the trading platform is allowed to trade without fees, which dramatically increased the volume of sales in RMB. Because Chinese exchanges added to the Commission, the trade volume of BTC / CNY in China fell. One of the advantages of a Japanese bitcoin trading is the fact that Japanese stocks do not charge commissions for transactions. It's a little alarming skeptics, since statistics JPY / BTC can be inflated for this reason.
Don't compare Chinese and Japanese market in terms of volume. Japan now is dominating the trading volumes as much 50%. Followed by USA. No fake volumes going on. Bitcoin ecosystem has been flourishing with a lot of money now specially coming from the Japan. We have to remember that Japan has a lot of money and it makes sense to them to just put in it bitcoin ecosystem since it is already a legal tender to them.
Definitely there is no fake volume generated in japan as china.They are already pioneers in bitcoin adoption,but lost interest in bitcoins due to Mt.gox failure.But now they have returned to bitcoin adoption by accepting bitcoin as legal payment.Trade volume would increase more in future.