Put the pork belly in a bowl, add shio koji and marinate for 30 minutes.
Heat a wok or pan with oil over medium-high heat. When the oil begins to smoke, add the garlic and meat and stir-fry until the meat is no longer pink.
Add the cabbage, bean sprouts, and carrots into the wok and stir-fry until they are tender.
Add the noodles, sake, water, soy sauce, and shio koji. Continue to stir until the noodles are well blended with the seasonings and completely cooked through. Transfer to plates and sprinkle aonori. Serve immediately.
You can keep the leftovers in an airtight container and store in the refrigerator for 3 days and in the freezer for a month.