Before the powering the console on, press and hold A + Select.
At the main menu, choose the first option. Then, on the next screen, select the second team's name to edit it. At the edit screen, press Down 2 times and Right 4 times and select that Japanese character. Then press Down 2 times and select the Japanese character. Finally press Right 4 times and Down 1 times and select Japanese character. Return to the main menu by pressing B, and press Select, Right and Left. If done right, the debug menu should appear.