Not entirely sure how authentic this is. I followed the shoyu ramen recipe from Joshua Wisseman.
If you’re worried about authenticity, probably compare notes with native cooks, but more importantly, check to see if the ingredients are correct. Very easy to get bastardised ingredients; as an example, living in an Asian country, I used to have a hell of a time getting the right herbs and vegetables for doing certain Western dishes with, and very common to get some pre-packaged “mix” of herbs instead.
Do Asian countries have Western markets the same way Western countries have Asian markets?
Perhaps unsurprisingly, yes, although the authenticity leaves something to be desired. Usually it’s just cheap stuff they can import in bulk quantities that appeal to westerners living abroad.
There was a common reddit post where European supermarkets would have an “American” aisle at their grocery stores and every time they post it, it’s literally just breakfast cereal, pop-tarts, peanut butter, and candy bars.