Make 4 openings in the flat side of the daikon with chopsticks or the tip of a knife. Insert a red pepper deep into each opening, so that the tip is level with the daikon. Set aside for at least 4 hours. The daikon's moisture will reconstitute the pepper and the pepper will have spiced the daikon. Grate the daikon, divide into 6 equal parts, and roll into a small ball. TO SERVE: Pour the pon-su (equal parts soy-sauce and lemon juice) and add a ball to each dish. garnish with onion and serve with sashimi.