Cutout mask using dynamically drawn lines?

I would like to achieve something like the image attached. Basically, to be able to "cutout" parts of a background image using dynamically drawn lines. (It doesn't need to be the Line Renderer tool, but anything that could allow the drawing of lines dynamically.) It would be nice to get this working inside the Canvas, but the regular 2D world space is also ok.



I need this feature for the "tutorial" section of a game I'm working on. Has anybody done this before or could point me to the right direction? Thanks.