I can only speak from working experience. I worked in Japan for 5 years and was probably in the only company that used English as the main working language. Several of my colleagues took a part time MBA in Japan because MBA's are not the normal recruiting path in Japan. Fluent to Business Level Japanese is a basic requirement and understanding of the work culture.
Just a few personal data points -
1) A high % of Japanese in the MBA program i went to and exchanged to were sponsored. (Recruitment of MBA's in Japan is rare)
2) I never met anyone from an MBA program working in Japan who was hired straight out of school (usually transferred there)
3) The 'foreigners' in Japan I worked with who took MBA's inside Japan avoided the local schools and went with McGill, they ended up in finance jobs afterwards, but they already have working knowledge of Japanese culture and very strong Japanese skills as well as many years experience working in Japan.
4) From my 'recruiter' friends who work in Japan, MBA is not highly valued outside of Consulting and Finance and both are mostly domestically focused which means almost fluent level Japanese required.
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