Ending
You can hold down the ESC key and 2 key when the game starts up and skip right to the end cutscene.
Aquarium screensaver
Boot the save disk (disk 5) to view swimming fish and the warning to boot different disk.
PSG
If the MSX has FM module, start the game while holding P to listen to the PSG music.
Continue
When the player dies, swap the game disk with an unused save disk (creatable with the utility disk), follow the further disk swap instructions on screen then the game continues as if the player has not died though several glitches occur so save the game to fix it. However this cheat is not confirmed to work because the exact timing to swap the disk is uncertain.