If you are preparing filming in Japan and searching for a local sound mixer who speaks English, I recommend Mariel Lohninger and Jeff Ruiz. They are reliable, easy to communicate and super skillful.
I have been working with Mariel Lohninger since 2015. He always does great jobs.
Mariel’s website http://tokyo-crew.co.jp/
Jeff Ruiz of H Media Group also provides us high quality sounds. He is very friendly, too.
Hope you have great visits and successful filming in Japan!