Have you checked
www.hlj.com,
www.arawasi.com and
www.abebooks.com yet? I had a quick search without luck, but maybe worth a shot.
Could it possibly the second book
here or
one of these series? I read somewhere the title is simply "Army Fighter Ki-61".
Somewhere else I found this comment, which excludes the above two titles but may help you in your search: "I have a copy of 'Army Fighters Ki 61'. It is no.93 in a series, I can't identify the publisher, but was authored by Watanabe, c.1983". Maybe it's nr.
98 in
this series?