I'd use ON1 Photo Raw on it instead of PhotoShop. Here's why, PhotoShop is unnecessarily complex and relies on LightRoom for some of the easier but possibly inadequate ways to solve the problem. PR combines both the features of PhotoShop (plus some improvements) as well as all of the gross and fine ("global" v. "local" adjustment of LightRoom.Several ways to try using PR2020 in increasing order of complexity:


1) First, using local adjustment brush with 0 feathering paint in light to match the lighter background
or
2)You could also use the clone stamp tool to replace the shaded part, or
3) You could use the paint with color option in local adjustments to simply paint over the unshaded granite color(s)
4) Use AI Quick Mask to mask out the entire granite background and replace with a background of your choice. (I like the idea of a blue sky with whispy clouds background so that Kilroy is like a sky-god.)

There are probably a dozen other ways to get what you want using PR but this should get you started.

If you're not familiar with Photo Raw 2020 it comes as a 64 bit only app for a 1 time charge and combines Photoshop and Lightroom features in one app with an easy to learn interface. Your Kilroy problem would be a good exercise to use to learn basic features of the program taught through hundreds of general and specific online videos. I don't use Lightroom or Photoshop any more and am glad I made the switch.