Kanto-style soba noodles

Wipe the surface of the kelp with a cloth.
Soak the kelp in water for 30 minutes.
Heat over low heat and remove the kelp just before it boils.
Add the bonito flakes and simmer for 1-2 minutes.
Strain the bonito flakes.
Add soy sauce, mirin and sugar to the dashi stock and warm it.
It doesn't boil, turn off the heat and it's finished.