As in question and image… how to achieve this effect?
I want to have scene with visible things only inside some area(which is brighter than everything else)
there are several 2d mask plugins that you can take a look in the asset store, i think you may need those.
To manage all light source, the easiest way is to render them all in a rendertexutre but it will be too big, unless your scene is very small. i think for better performance, you need to write your own component and shader, so that when you get under a light source, you only use that light source to do masking