To make stock: To remove excess fat, cover pork bones and belly pork with water, bring to a rolling boil, drain and rinse. Add 3 quarts fresh water to bones and pork; bring to a boil. Cover and simmer 30 minutes. Skim off foam and simmer another 30 minutes.
Remove bones and pork. Cut pork into 3-by-2-by-1/4 inch slices and set aside.
Add bonito flakes to broth in pot and boil 2 minutes. Strain; discard flakes. Add salt and soy sauce; simmer 2 minutes.
To season pork: Combine seasoning ingredients in a skillet and bring to a boil. Add sliced pork from the stock pot, turning occasionally until well-glazed. Set aside.
Pour boiling water over soba and drain. Put noodles in bowls; add stock. Garnish with pork, kamaboko, onions and red ginger. Serves 4.
Approximate nutritional information, per serving, per 1/2 cup: 530 calories, 30 g total fat, 11 g saturated, 80 mg cholesterol, greater than 2,500 mg sodium, 24 g protein, 40 g carbohydrate.*.