Combine the seasoning ingredients (mirin, soy sauce, dashi powder, and water) in a microwave-safe container and heat at 600W for 30 seconds. Let it cool.

Boil water in a pot, add a pinch of salt, and blanch the kakisai greens starting with the stems for 30 seconds, then the leaves for 10 seconds. Drain and cool in cold water.

Cut the kakisai greens into 3–4 cm pieces.