After years of travel to Japan, and now living in Japan, and having the ability to speak and read Japanese, I can tell any young person that learning Japanese will not help you crack the Japanese business matrix in any majorly meaningful way. Understand it? YES. Enter it as an equal participant? NO. If you want to do business in Japan from overseas, hire a Japanese person, you'll save yourself a lot of time and annoyance. Of course if you are into self flagellation, go for it. Bottom line, outside of Japan, Japanese is almost totally useless and won't "really" open any big doors in business as most Japanese ready to deal with you in global business style will probably insist on speaking English anyway. I'm sure that business-to-business "within" Japan there are numerous exceptions to what I'm saying, but in regards to doing specifically 'global' business, I stand by my assertion.
On the other hand, learning Chinese will open an entire new realm for your business pursuits, as they generally value business/cash over cultural rigidity. Your time is better spent on Chinese.