This is a simple cold miso soup which doesn't contain horse mackerel. It's light and refreshing, so you'll just want to eat more and more.
I got this idea from a cold soup recipe. I added leftover miso soup to make my own version.
The dashi stock is nice if you use iriko (dried sardine) powder, or if you grind the dried sardines with a mortar and pestle before adding.
Enjoy Japanese food around the world.