In a large pot or Dutch oven, heat the sesame oil over medium heat until hot.
Add the onions, carrots, celery stalk, shiitake mushrooms, garlic, salt and kombu. Cover and cook for about 10 minutes on low heat until the vegetables are softened.
Add the wakame and arame and continue to cook covered for about another 10 minutes.
While the soup is cooking this is a good time to peel and grate ginger. Squeeze out the juice of the ginger with a cheese cloth or fine strainer and set aside in a separate bowl.
Add the water and bring to a boil. Reduce the heat to a low simmer uncovered for 10-15 minutes.
Remove pot from the heat and let the broth stand for 5-10 minutes. Add the ginger and lemon juice.
Temper miso in bowl by mixing it with 2 cups of broth. Then add the tempered miso back into the pot.
To finish, add green onion and sesame seeds (optional)
Serve hot. Enjoy!