making this stuff is kinda easy if you get it, just some basic tinkering with ps filters and this concept:
-the animu grill that you're going to use must fit in the background, and needs at least decent shadowing.
You can cover the lack of shadows on the base image on rainy/night backgrounds, but on day you're going to need a nice render.
Also, you have to use some 3D light, but first, balance the colors.
Extra points if you're able to do this without using kyoani grills and extra 4k blurry forest/Russian backgrounds.
Going to dump the good ones that I made for some chilean group.