To access Super mode Shining Gundam pick Shining Gundam and any other opponent in VS. mode. Beat Shining Gundam 21 times in a row.After the 21 time press start on the joystick that Shining Gundam lost when choosing him for the 22 fight. You will here him say something in japanese confirming that the code works.

For super mode Master Gundam, follow the same instruction but he has to lose 31 times.