Below are a couple of links to other organisations that may be
able to help you find your way to the mountains...
Yama to keikoku (山と渓谷)
Yama to keikoku
(mountains and ravines in English) publish the widest range of books
and magazines on walking and climbing in Japan, including the
eponomously named yama to keiko.
International Adventure Club (Tokyo)
To date I have never been to a meeting of the
International Adventure
Club in Tokyo but it's been around for such a long time it looks
well worth a visit.