Cut the fish cakes, radish, and green onion into bite-sized pieces.
Add water, kelp, and anchovies to a pot to make broth.
Strain the broth and pour it back into the pot.
Add the prepared radish and boil.
Once the radish is cooked, add the fish cakes and onion.
Season with soy sauce for soup, salt, and pepper.
Add the green onion and bring to a boil once more.