Put a sheet of kombu, the corn cob, and water in a saucepan and bring to a boil over medium-high heat. Once mixture is boiling, remove the kombu. Cook another five minutes and remove the cob.
Note: bonito flakes are not necessary in this recipe because the corncob makes a rich broth, but for extra flavor, you can add 1/4 cup of bonito flakes with the corncob and strain them out).
Reduce heat to medium. Add the corn kernels and cook for about one minute more.
Add okra and turn off the heat immediately. Add miso paste, stirring well until it is dissolved.
Serve hot in individual bowls, garnished with green onion.