The kick of the wasabi is tempered some by the sweetener. The proportions given are just a guideline.

1/4 c unseasoned rice vinegar or cider vinegar
1 T  wasabi powder or dry mustard powder; or 1 T freshly grated or prepared horseradish
1 – 2 t sugar, agave, or liquid honey
2 T water
1 T soy sauce
1 1/2 c peeled, shredded or diced kohlrabi
1 c (peeled) shredded or diced daikon or other radish
1/2 c (peeled) shredded or diced carrot
2 T (red) onion, finely chopped

1. Mix together vinegar, wasabi powder, sugar, water, and soy sauce in a large bowl.

2. Add the vegetables, toss to coat. Chill (or not) for an hour or so before serving.