A comment about the "side hustle" idea - a lot of that in my experience was just about keeping a spirit of exploration and an open mind for recognizing opportunities that occur naturally. Through this I have discovered things I love, learned a lot about, and then turned into an actual money maker or at the very least a satisfying hobby.
Waseda is well respected and has a strong brand in Japan, it’s a leading institution and a lot of companies hold a Waseda degree in high regard. I have little first hand knowledge about the MBA program other than a professor I had at Hitotsubashi ICS who now teaches there (he was excellent). I hope this helps, best of luck on your MBA journey!
Step 1: leave Japan. These examples aren't people who made it in Japan. They just left and started over. Hopefully you didn't set down any roots in Japan, because it's about the mindset of abandon everything start over and don't come back.
You raise an excellent point, Joe. My two examples are limited to those that left, there are many that stayed and developed satisfying careers in Japan.