Make soup first. In a large pot, put water and chicken wings, and let boil. After boiling for a few minutes, remove any scum and fat that come to the surface of the soup. Add garlic, ginger, and green onions, and cook covered for 40 minutes or so. Add some water if losing too much liquid. Strain the soup, but save chicken wings and set aside. Season with Soy Sauce, Sake, Mirin, salt, and sesame oil. (You may need to adjust the seasoning if you added water earlier.) Keep warm on low heat, covered.