How can i shader transparent Objects together?

First i am sorry for my bad english and shader skills! In my little game I have a character, which can run around. If he runs behind a Wall, this should get transparent. After searching and testing a while I got a shader can do this. Now my Problem: If the Player is behind the wall and under the roof, both get transparent, like they should, but you can clearly see the area they connect each other. How I could do that you cant see that? Connect the 2 objects temporary? Shader them somehow together as one object? Or just few lines more code in my shader? Here the problem:

My acctual Shader is here:

 Shader "Transparent/CastShadow" {
     
   Properties {
 
     _Color ("Color", Color) = (0.9, 0.9, 0.9, 1.0)
     _MainTex ("Base (RGB)", 2D) = "white" {}
   }
 
   SubShader {
     Tags { "RenderType" = "Transparent" "Queue" = "Transparent" }
     Blend SrcAlpha OneMinusSrcAlpha
     Cull Off
     LOD 200
  
     CGPROGRAM
     #pragma surface surf Lambert
  
     fixed4 _Color;
     sampler2D _MainTex;
  
     // Note: pointless texture coordinate. I couldn't get Unity (or Cg)
     //       to accept an empty Input structure or omit the inputs.
     struct Input {
       float2 uv_MainTex;
     };
  
     void surf (Input IN, inout SurfaceOutput o) {
       o.Albedo = _Color.rgb;
       o.Alpha = _Color.a;
     }
     ENDCG
   } 
   FallBack "Diffuse"
 }

ps: I normely programm in C#