Soak seaweed in cold water for 10 minutes, then drain.
Cut tofu into bite-sized pieces.
Pour water into a pot and bring to a boil.
Once boiling, add the seaweed and cook for 2–3 minutes.
Add the tofu and bring to a boil again.
Dissolve miso paste into the soup and simmer over medium-low heat for 2–3 minutes.
Taste and season with salt if needed.
Serve the finished soup in a bowl.