The article I saw said the brokerage firm couldn't confirm the info. Yet, nothing wasn't mention about any tax returns.
Also, any trader on the Tokyo Stock Exchange that trades size like that are given a special ID as a professional trader. Simply, he's not a retail trader.
Ok maybe I shouldn't have used the term retail trader.
From now on "individual investors" guys who trade on their own behalf and take all the profits. They can have whatever qualifications/special id/seat/office etc They just have to work for themselves, trade their own money and take all the profits.