Here's another book on personas and user centric design for you to recommend to your Japanese colleagues and friends. The Japanese title roughly translates as:
It was written by Hiroki Tanahashi – He and I are both members of the Persona Consortium, which seeks to promote the use of personas in Japan. He writes an excellent blog and various other articles about marketing and web design.
The book hasn't been released yet – but I've already placed my order with amazon…
The purpose of the book is to explain specifically how personas can be applied in Japan, with concrete case studies.