When we eat Japanese food, garnish or relish is sometimes set the food aside. It is not only for taste but other meanings are included.
For example, in case of eating Sashime (row fish), shredded Japanese radish (Daikon), labiate or seaweeds is set with it on the plate. It is especially called "Tsuma". Daikon lets the Sashimi's taste exaggerate. Tsuma has effect to sterilize microbe in our mouth. This is called "Dokukeshi" effect.
Wasabi is one of Japanese relish, Yakumi. We dissolve wasabi into soy sauce. This is for Dokukeshi. Considering to the taste, wasabi is essential seasoning. When you eat Sushi, sour ginger, "Gari" is put on the plate. This is also same effect.
There are a lot of combinations to better the taste in Japan. Almost combination has meaning for the taste or effects to our bodies. Ancient Japanese people wouldn't know about scientific evidence for these effects. However, the wisdom that were gotten by their experiences lives in our food culture.