Trim fat from oxtails. Rinse and pat dry. Set aside. Chop onions, carrots, daikon radish, and thinly slice mild pepper. Set aside.
In large cooking pot, add oil, heat onions, carrots, ginger, radish, and spices until onions are tender. Add oxtails. Pour in enough water to cover oxtails.
Bring to boil, then reduce to simmer for 5 hours covered or until oxtail meat is easily removed from the bone.
Strain soup liquid into a new pot. Set aside vegetables and oxtail. Add noodles to soup liquid and cook according to package directions until as tender as you'd like.
Meanwhile, remove oxtail meat from bone. Add vegetables back to soup liquid with noodles. Fill bowls with soup, add oxtail meat, top with cilantro, green onions or chives and mild pepper slices.