To my knowledge, the NTA does not list directors or ownership.
METI (Ministry of Economy, Trade and Industry) has a portal to potentially display that information, but for private companies it may be missing, and thus the results may be no better than NTA's records: https://info.gbiz.go.jp/
METI (Ministry of Economy, Trade and Industry) has a portal to potentially display that information, but for private companies it may be missing, and thus the results may be no better than NTA's records: https://info.gbiz.go.jp/
Public entities (which Big River Services Japan is not) can be searched through the JPX (Tokyo Stock Exchange): https://www2.jpx.co.jp/tseHpFront/CGK020010Action.do