This is a known issue related to The Symbiant's game engine (Ren'py) when launched on very old hardware or outdated graphic card drivers.
To fix it, you can try the following steps:
- hold the SHIFT key while clicking the game launch button
- a grey screen will appear instead of the game, that's normal
- select "Force GL2 Renderer", then "Quit"
- Restart the game.
- If the issue persists, go to that grey menu again and select "Force ANGLE2" Renderer" instead