I've been living in Japan for 9 years, married to a japanese for 6 years.
I do not have a good answer for you, still trying to figure things out myself, but here's what I've done:
- a large amount of my money is on a schwab brokerage account in the US, which my (American) company opened for me a while ago. That account is 100% stock. I think that, not being an american citizen and not living in the US, I am not allowed to get any bonds. They have "bond based stocks" which don't have the same guarantees as bonds, but seem good enough, I'm thinking of buying some of those. Overall, by putting my money in on of schwab's ETFs (SCHB), I've seen good results so far, I just need to diversify a bit more
- My wife and I largely disagree on where and how to invest money. She does not trust the stock market, and the historical proof that it performs better than anything else does not convince her. The Japanese haven't seen investments actually generate any sort of benefit/interest in years. It is very difficult for them to understand that there exists ways to get a reasonably safe 4% return on investment. Bottom line is we sometimes have to compromise. she opened a bunch of JP insurances (life insurance, cancer/heart attack insurance) and a fund to get our kid through college. All of these are sub par investments (the disease one is a pure waste, nothing's coming back unless I actually get cancer) but it makes her feel safe. They also give back more than having "just" the money in cash, so it's still a better deal than keeping cash (with the huge counterpart that in the college fund thing, the money is locked for about 15 years...)
- I got scammed by some "asset management" company that sold me an offshore life insurance (RL360, a.k.a Royal London 360). DO. NOT. DO. THIS. All these life insurance companies are at best a very poorly optimized investment strategy, at worst you will actually lose money. They are easy to spot, but you have to know about them. 101% return guarantee, obfuscated fees, many red flags should have warned me but I was so happy to have found the "expat loophole" to prove my wife that investing offshore was better than investing in Japan... I lost about 2M Yen, and I am in the process of cancelling that thing now. It is rampant in Tokyo, so be careful.
- Everything that is remaining on our bank accounts goes into short term investments: Our bank is shinsei, they have this 2-week investment thing. Brings close to no interest, but better than 0.
Bottom line: try to invest as much as possible in the US stock market, this is what has been both the most successful and the most "safe" for us so far. You just have to find a balance where she's confident. I would suggest you convince her to put 20 million yen at the same place you have your 100K USD, assuming you are happy with your investments so far. The remaining 10M she can keep in cash for safety, or invest in one of these low return things I mentioned above (insurance, college fund for kids, or short term savings with your bank)