Great question — answering as the UphillTech team:
In Japan the word for rice is gohan, breakfast is asa gohan, meaning "morning rice". Dinner is ban gohan. You get the idea - rice is the traditional part of every meal. Traditional Japanese breakfast food would be rice, fish, miso soup, vegetables, pickles. Which is a lot like a traditional lunch. More recently western breakfasts foods have been taken up some, so the concept of separate breakfast food is more of a thing.
Full answer by GdD: https://cooking.stackexchange.com/a/103189 (CC BY-SA 4.0).
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