Finding those in Japan is another matter. Corn is available (I’m growing it this year as well) and I do ocassionally get corn tortillas but those are basically a luxury item. I even looked into possibly growing sorghum. I use tapioca starch in some recipes for texture and flexibility, but it’s expensive. I do eat oats as well, but those are getting expensive and they mainly sit in my mind as something to be eaten on their own not as part of a meal.

For corn and oats, I can’t think of those as the main carb in a meal; it just doesn’t work for me (except, as mentioned, when oatmeal itself is the meal).