I just finished the demo and as others have pointed out, is just about perfect. A couple of things I'd like to see with the game are;
• Having a native Japanese voice actor (not the high pitch ones)
and/or
• Having a native Japanese voice actor speaking English
I'm sure the current voice is only temporary, but it really does detract from some of the immersion.
Secondly, some of the language used in the voice over and letters aren't very period correct. Such as "...and I've messed it up" just doesn't feel right.
But apart from those, a very well done!