The source seems http://www.warbirds.jp/kakuki/kaksei/ki115-2.htm
(the kakuki collection is a great collection of fakes, including many twin-boomers presented in my book "The end of Forked Ghosts")
Translated in English, this page is :
http://translate.google.fr/translate?sl=ja&tl=en&js=n&prev=_t&hl=fr&ie=UTF-8&layout=2&eotf=1&u=http%3A%2F%2Fwww.warbirds.jp%2Fkakuki%2Fkaksei%2Fki115-2.htm