I’m no expert on this but I think I understand the logic of what has to happen here. So you want a sort of X-Ray vision? So that when a character is blocked or occluded by another object, it has a specific look (shader).
So you will need 3 materials:
1.) Material to apply to objects that you want to be seen through
2.) Standard material for character
3.) X-Ray material for character
Apply the standard material to the character
If the character’s material is further than the object’s material that is occluding it, apply the X-ray material to the character, else keep the standard material on the character.
There are also some sorting settings you will need to apply. I’ll try to do some research.