[noodle]

I don't know why you guys assume ALL MBA's and higher education degrees are so complicated and requiring a very high level of language. MMM, if you have any problems with an MBA, it will be because of the content, not the language! There are dozens of MBA degrees that have lots of emphasis on English in every country. The second best Business school in France (lets say, equivalent to Yale or Harvard etc) accept foreigners with VERY limited French to their MBA course. I know three people that done this last year. A Vietnamese, A Chinese and a Brazilian!

To the OP; If you're set on going to Japan, which honestly I don't understand especially for an MBA, then of course it's better to know the language to a decent level. Just because you can work on a limited level, it doesn't mean you should. My three friends had to work 10 times as hard as their classmates on the modules that were purely French.

I think you should ask yourself why you want an MBA and why in Japan! When you have answers that will be accepted at an interview a top school in Japan will give, then you should start thinking about the how you'll be able to get there!