I replaced the tuna with salmon in this fresh spring salad.
In Japan there are basically 5 types of soy sauce (soy sauce is shoyu in Japanese): koikuchi, usukuchi, tamari, saishikomi and shiro. Of these, we mainly know the first in the Netherlands/Belgium: koikuchi. And often under the name of the most famous brand: Kikkoman. Koikuchi soy sauce (fermented soybeans with wheat, water, salt and yeast) is made from equal parts of soy and wheat. Because of the larger quantity of wheat, it is softer and less salty than the Chinese light soy sauce, but very similar. So you can easily replace one with the other.
How to use?
In Japanese cuisine in marinades, in dishes or as a dip. Can serve as a substitute for Chinese, light soy sauce. And can be used as a basis for making sweet soy sauce. Keeps in the fridge for a long time.
From: Robin's website http://www.aziatische-ingredienten.nl