In a small saucepan combine the soy sauce, the vinegar, the gingerroot, the sugar, and pepper to taste and heat the mixture over low heat while preparing the fish. Pat the fish dry and season it with salt and pepper. Have ready in separate shallow dishes the cornstarch, the eggs beaten with the salt, and the bread crumbs combined with the sesame seeds. Dredge each fillet in the cornstarch, coating it thoroughly and shaking off the excess, dip it in the egg mixture, letting the excess drip off, and dredge it in the bread crumb mixture, pressing the mixture to help it adhere.
In a skillet large enough to hold 2 of the fillets comfortably heat 1/4 inch of the oil over moderately high heat until it just begins to smoke, in it fry the fillets, 2 at a time, reheating the oil between batches, for 45 seconds to 1 minute on each side, or until they are golden brown, and transfer them to paper towels to drain. Transfer the fillets to 4 heated plates, bring the soy sauce mixture to a boil, and spoon it over the fish.