Bring a large pot of salted water to a boil. Cook the noodles according to the package directions. Drain and rinse under cold water.
In a large saucepan, combine the chicken broth, garlic, ginger, mirin, tamari, and fish sauce. Bring to a boil. Reduce heat and let simmer for 10 minutes. Add the chicken and continue to simmer until the chicken is heated through, about 5 minutes.
Season to taste with salt and pepper. Serve the soup garnished with green onion and cilantro.