Wash the potatoes and boil them in their uniforms in boiling salted water until they are half cooked.
Cool and clean.
Peel and chop the onion. Also prepare the olives and olives, drain the liquid from them.
Heat the vegetable oil in a frying pan or saucepan, add the potatoes, onions, olives and olives, and cook over medium heat for 5 minutes. Then add the Kikkoman soy sauce and water and cook for another 15 minutes.