Japanese foods are very simple to make, though some of the ingredients may not be so easy to find in Norway. The primary seasonings necessary are soy sauce (easy to find), mirin (a sweet cooking sake), sugar (again, easy to find), konbu (thick seaweed), dashi (a soup stock made from dried fish), and miso paste (used to make miso soup, but also important in other dishes).
You can make a Japanese flavor dish using cabbage, onions, thin sliced beef, mushrooms, hard boiled eggs, or other ingredients which you think might go well.
First, you must make the basic stock, which is called dashi. You normally take a handful or so of small dried fish and boil them in water for just a few minutes. As the stock boils, a foam will appear on the top, it is important to scoop this foam off and discard it.
Once the stock is done, you strain it with a fine strainer or filter of some type to end up with a clear broth. To this broth you will and the konbu (dried sea weed), mushrooms, and then the cabbage, onions, beef, etc. The dish you are making is generally known as "nabe", which is cooked and served on the tabletop in Japan.
As the vegetables and meat are cooking, you add some miso paste, soy sauce, mirin, and some sugar. Add these until you get the taste you like. The flavor should be subtly like teriyaki sauce, salty, but with a touch of sweetness to it. Some people remove the konbu before eating, others like it. I have no preference, but konbu adds a flavor to the dish.
You can find any ingredients you need online here:
Mitsuwa Marketplace -in the "online shopping" section.