The Japan Association of Corporate Directors has released a report outlining guidlines and standards for nominating independent directors. The report is in Japanese and is available (along with a summary) at the following links:
http://www.jacd.jp/news/odid/110523_post-60.html
JACD 取締役会規則における独立取締役1の選任基準 (モデル）http://bdti.mastertree.jp/f/bz0pfxalｖ
JACD 取締役会規則における独立取締役1の選任基準 (モデル・解説）http://bdti.mastertree.jp/f/c4keipd3
The Board Director Training Institute (BDTI) is a "public interest" nonprofit in Japan dedicated to training about directorship, corporate governance, and related management techniques. It is certified by the Japanese government to conduct these activities as a regulated nonprofit. Read a summary about BDTI here, and see a menu of its services for both corporations and investors here.