Follow the instructions to get the corresponding result:
Choose costumes: press A or X on the character select screen.
Shu Generals: WHITE, BLACK, X, Y, WHITE, R, L, BLACK on the main menu.
Generals: Hold L and R, then press WHITE, BLACK, Y, X, X, Y on the main menu.
BGM Test Option: L, WHITE, Y, R, WHITE, BLACK, X, Y on the main menu.
Edit Option: X, BLACK, Y, WHITE, L, R, WHITE, WHITE on the main menu.