This is a paid asset, but now you can download See-Through System for FREE, but please remember this package is provided only for learning purposes or to be able to test before buying the product, NOT FOR COMMERCIAL PURPOSES.
Detail this asset from Unity Store: Original Link
See-Through System v1.8c (Latest version)
See-Through System provides an easy and highly configurable way for implementing partial transparency in your projects. Use it to make your character visible behind obstacles in isometric RPGs or strategies, see enemies behind walls in shooters or improve any other projects requiring handling of visibility obstruction.
Latest version requires Unity 5.6 or higher.
Windows demo download
MacOS demo download
See-Through System is completely shader independent, so you don’t need to change your materials, shaders or touch your scene objects at all for it to work.
You can control see-through parts rendering by enabling image effects only for these parts, using depth sensitivity to fine-tune transparency toggling, using Outline or Hologram built-in shaders, or using your own shaders with help from “RenderWithShader” setting.
Despite usage of multi-camera rendering, there’s option for preserving original depth texture, so your other image effects won’t be affected by it.
Tested on Android and iOS devices.