Since GMATclub helped me a lot, now it is my time to help out someone in this forum.
Rob, I think I am one of the right persons to ansewr your question because I am a 30 years old Japanese guy, working in the Investment Banking Department in a domestic securities firm. Plus I was a career switcher from private banking to investment banking several years back.
My bottom line is that it is not a right choice to seek Japanese MBA degree.
First, Japanese MBA programs are not accredited by AACSB except for Keio, Nagoya and Temple University Japan campus. It translates that most of the Japanese MBA programs don't meet the minimum requirement of what AACSB evaluates. I am not saying that their quality or fuculty of study are inferior in the world but they might be different from what you could learn from AACSB qualified schools.
Second, Japanese MBAs don't increase a chance to land in banking/accounting industry. Japanese companies prefer linguistic ability over MBA. I have a couple of foreign friends working in M&A in demestic I-banks. They've come from different industries such as electronics or telecommunication industry without MBA but they show strong command of Japanese and do some research jobs for their industry. In the meantime, I know there are several Japanese-free M&A bankers or Captal Markets bankers with MBA degrees from US top schools. You can apply to Japanese I-banks in the US after MBA and show your linguistic ability to transfer to Japan headquarters. Regarding accounting firms in Japan, they consider CPA licenses necessary than MBA degree.