METI has got several councils or study groups working on themes related to corporate governance, acounting, disclosure, shareholder engagement,and CSR Policy. Most of them are summarized (with materials) here:
http://www.meti.go.jp/english/policy/economy/corporate_accounting/
andhere:
http://www.meti.go.jp/english/policy/economy/corporate_accounting/corporate_governance_02.html
http://www.meti.go.jp/english/policy/economy/corporate_accounting/pdf/121211_03.pdf
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.