Hyokkori Hyoutanjima: Nazo no Kaizokusen - Cheats & Codes
Area Skip - While playing, press Up + B on controller 2 to skip to the next area.
Sound Test - At the password screen, select the first password space and press Up 21 times. Then select the second password space and press Up 1 time. You can now press A on controller 2 to hear the music and B to stop it. If you keep pressing Up to select other Japanese characters, you can listen to more music.