what's the difference in the demo and the full the game
The free(demo) version is always one major update behind.
Major updates add - A new story path for one of the characters, ''animations'' related to that path, new locations, etc.
In the demo - the last path added was - Yasuka's Love path.(0.5.9)
But in the latest version, you can already select Yasuka's Corruption path.(0.6.91)
So, right after the new major version(0.7) got released - Yasuka's Corruption path will be available for everyone.