https://youtu.be/Z8JLfr2s3DQ (My favorite Korean food chef on YouTube)

Very good with this tempura sauce:

Add ½ tsp Hondashi crystals to 300 ml water. (Buy in Asian market - I keep in fridge for miso soup)
Bring to a boil and add 90 ml or soy sauce and 90 ml mirin
Simmer 3 minutes
Just before serving at grated daikon, if desired.