Place the chicken bones in a large pot with the water, pork, garlic, ginger, and green onions after giving them a cold water rinse.
Bring to a boil while skimming off any surface-level dirt. Reduce the heat, cover the pot, and simmer for about two hours.
As soon as you've added the soy sauce, sake, and mirin, cover the pot and let it boil until you're ready to serve.
In a big pan, combine the ingredients for the chashu sauce. Over medium heat, add the meat and then bring the mixture to a boil. Once the meat is covered with a lid, lower the heat to low and simmer for about 30 minutes, flipping the meat occasionally, until there is very little liquid remaining.
Keep an eye on the liquid simmering until bubbles begin to develop while removing the lid.Once the sauce has completely covered the pork, take it from the pan and slice it thinly.
When you're ready to serve, prepare the ramen as directed on the package. Add the noodles, pork, bamboo shoots, soy-marinated eggs, green onions, and broth to six bowls.