Akira is based on the 1988 movie, which in turn is based on the manga. It's a rather mediocre visual novel otherwise and one of the few games based on Akira that actually got a release.
There are A LOT of unused graphics and some unused messages (See the talk page.)
Password any Time
Normally, during the game, you can get a password only for specific checkpoints (usually at the beginning of the new scene) and only after getting a Game Over. The password system in this game much more complex and has a lot of redundancy, likely so it could save a lot of game parameters/triggers and event flags. Obviously, all this stuff couldn't be used.
However, there is a working debug leftover that wasn't disabled. This allows you to quit the game any time you want and write down the full password exactly for this particular place. In order to use it, any time while the action selection menu is displayed, press A on Controller 2. When asked, choose either to play from the beginning of the current scene or get a password and quit.
One more debug leftover has been disabled in the released version. Use the Game Genie code XTXKVYAV to re-enable a Scene Skip feature. During the game, press B at any time on Controller 2. Doing this on the game over or the password screens sends the player to the ending screen (both the passwords or the game over screens are parts of internal scene 17; the ending scene is 18 and it is the last scene to skip to).
Messages Fast forward
Use the Game Genie code GEVENXGK to re-enable fast forward messages by pressing A on Controller 1.