Put all the ingredients except for ★ into a pot and bring to a boil. Turn off the heat and strain through a strainer or some gauze.
Done! Add the ★ ingredients to taste and enjoy with some tempura!
Story Behind this Recipe
I wanted to have some delicious tentsuyu with piping hot tempura!
Don't let it boil too much! Be careful not to burn yourself when straining out the bonito flakes. I highly recommend adding grated daikon radish. Add sugar to taste. My family prefers this on the sweet side, but you can omit it if you like.