You don’t have to buy expensive special ingredients / seasonings
If you are already interested in Japanese kitchen, you might have been to a Japanese / Asian supermarket to get some ingredients or seasonings that is mentioned in a recipe you found. I have a favorite Japanese / Korean supermarket in Amsterdam. However, you might agree to the biggest problem: the products in those supermarkets are super expensive!
What I buy at that Japanese supermarket is mostly Japanese rice (grown in either in Italy or Spain) and Japanese curry blocks. Some years back, I was also buying soba soup, but I don’t buy it anymore. Why? I don’t eat soba (buckwheat noodle) anymore? Yes I eat them, and I make the soup by myself!
You can make most of the special-named Japanese ingredients at home with ingredients that a local supermarket has.
Recipes for substitute of Japanese Seasonings
Cooking Sake
Just buy a bottle of reasonable white wine. I use the cheapest white wine that is in a carton packaging.
Mirin
Mirin is similar to sake, but it contains more sugar and lower alcoholic. It gives luster on the dishes. You can use white wine and sugar (ratio 3:1) instead of mirin. For example, mix 3 table spoons of white wine and 1 table spoon of sugar. This is it.
Dashi
Dashi is a soup broth which Japanese recipes heavily use. In Japan or Asian supermarket, you can buy dried powder/grained soup stock. In a traditional way, you can make dashi with water, dried bonito flakes and dried kelp seaweed, but those ingredients are hard to get. The taste can be a little bit different, but I use bouillon sometimes.
Miso & Soy Sauce
As far as I know, there is no other ingredients that substitutes miso or soy sauce. You can mostly get soy sauce at a local supermarket. I recently saw miso at the nearest supermarket in the Netherlands.