Listening to two westerners talk about rice to someone from Japan has, for me, the surrealism of listening to someone who lived their entire life in Phoenix, AZ talk to a native Norwegian about x-country skiing. But I digress ...
The only way to know how it will work for you, Madison, is to (carefully) try it and find out. And it may take time to work out your details. Also, those details may change with time depending on if/how you body might change in the future.
But I agree with you that working out a diet that doesn't involve rice in Japan is not a rational starting point. I'm not sure if I could come up with an analogy for the US simply because there seem to be so many options in the US. This is more like asking someone to give up bread in a place where there pretty much isn't anything but bread. I realize that is also not accurate. But maybe closer?
I am curious what the CDEs (Certified Diabetes Educator) in Japan suggest for the meal plans. I never thought to wonder before. Have you talked with anyone who has told you anything which was of use to you in this area?
For whatever it may be worth, here is a link to an article which may be of some help. (Not for your train trip & lunch but maybe over time).
High Blood Sugar After Meals And What To Do About It
If that one article is not helpful, there are others out there. Try Googling about.
The main tool used to limit a postprandial spike is probably the pre-bolus. However, that is a tool which you want to be careful of given your concern about hypoglycemia.
If you decide you want to work harder on limiting your highs after meals, it helps to have a CGM. And not just because it can give a better picture of how your BG behaves after a given meal. It also makes it much easier to "see" when & how quickly your insulin is starting to take effect. This can make pre-bolusing safer IMO.
BTW, if you do go high don't panic. Short term, it's more frustrating than dangerous. And I doubt you will go that high since you still produce some insulin.
Yesterday I apparently did not reconnect my pump to my infusion set correctly after I showered. Later, I ended up with a BG meter reading of 582. Ooops.
I survived, though I felt lousy until I was able to fix the problem.
-iJohn