Freshfield's Guide for Directors of Subsidiary Companies in Japan is well worth reading if you are adirector on a subsidiary company board and have never learned much about your duties and responsibilities under Japanese law.
http://bdti.mastertree.jp/f/86mei0dh
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.