camera – Shader to Show outline, and transparent back

I would like to implement in my game a kind of occlusion for back wall. I want, when my camera is inside a wall, to be able to "see" the beginning of the wall, with a transparency effect or watever.

Here is my initial situation:
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And here's what I'd like to find:
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Is it possible ? How can this be done? with shader? with some sprite with transparency and nice use of raycast?