Collect 45 fortune dolls. This unlocks Boss Mode in the options screen.
Unlock I Am Impact in Sound Test
To unlock ''I Am Impact'' in the sound complete the first robot battle.
Unlock the boss mode and beat it to recieve a hidden image
Fight Benkei as Ebisumaru to throw the Achilles' Heel at him faster. During the battle, Benkei will threaten to blast you far away. This is a lie; he will knock you into the river next to the bridge where he is standing. There is a ladder available to return to your previous location.
Press R + C-Up to enter first person mode. You will be invincible, but when you come out you can get hit. Since they usually stay by youm this is best used on the tiles that fly at you. This does not work in Boss stages or with impact.
Unlock Gorgeous My Stage in Sound Test
To unlock ''Gorgeous My Stage'' in sound test you must save the game right before the last robot fight.