Boil the buckwheat noodles in boiling water.
Rinse the boiled noodles in cold water and drain.
Finely chop green onions and seaweed.
Mix tsuyu sauce with water to make soba broth.
Place the noodles on a plate and top with garnishes (green onion, seaweed).
Serve the broth separately and dip the noodles before eating.