It's true that the MBA degree didn't have the same value in Japan that it has in countries like the US. However, things seem to be slowly change on that front...slowly being the keyword.

We wrote an article that might help (read it here --> MBA degree in Japan reclaiming respect

Knowing Japanese is surely helpful when you are talking to potential recruiters.

Having said that, don't assume that the situation has changed dramatically. Try getting in touch with international students studying in your target schools and find out what they say about the pros and cons. Then take a call.

Good luck!