Rehydrate the dried wakame in plenty of water. Chop the green onion into small pieces.

Boil a large pot of water and add the soba noodles. Stir gently to loosen the noodles. Once boiling again, reduce to low heat and cook according to the package instructions. Wash the noodles under cold water and drain.

In a pot, combine the men-tsuyu and water. Heat over medium heat until boiling.