The Oanechan Bara
When "Push Start Button" appears at the title screen, quickly press Up, Down, Up, Down, L1, R1, L2, R2, L3, R3, Up, Down, Up, Down, L1, R1, L2, R2, L3, R3. If you entered the code correctly, you will hear a sound. Enter quest mode to unlock all secrets.
Successfully complete stage 6 on the normal difficulty setting in story mode to unlock the hard difficulty setting.
Successfully complete stage 6 on the hard difficulty setting in story mode to unlock the violent difficulty setting.
Successfully complete 6 quest mode missions in story mode to unlock Costume 2.
Successfully complete 8 quest mode missions in story mode to unlock Costume 3.
Successfully complete 10 quest mode missions in story mode to unlock Costume 4.
Completely fill the "????" meter to unlock Costume 5.
Successfully complete stage 6 on the violent difficulty setting in story mode to unlock Costume 6.
Successfully complete 2 quest mode missions in story mode to unlock Wallpaper 2. Press L1, L2, R1, or R2 at the mode selection screen to cycle through the wallpaper.
Successfully complete 4 quest mode missions in story mode to unlock Wallpaper 3. Press L1, L2, R1, or R2 at the mode selection screen to cycle through the wallpaper.