Apparently "Heroes" has a second e in it.

Chaos-Heroes-Online-Extractor.csproj

@@ -3,7 +3,7 @@
   <PropertyGroup>
     <OutputType>Exe</OutputType>
     <TargetFramework>net6.0</TargetFramework>
-    <RootNamespace>Chaos_Heros_Online_Extractor</RootNamespace>
+    <RootNamespace>Chaos_Heroes_Online_Extractor</RootNamespace>
   </PropertyGroup>
 
 </Project>

Chaos-Heroes-Online-Extractor.sln

@@ -3,7 +3,7 @@ Microsoft Visual Studio Solution File, Format Version 12.00
 # Visual Studio Version 16
 VisualStudioVersion = 16.0.34407.143
 MinimumVisualStudioVersion = 10.0.40219.1
-Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "Chaos-Heros-Online-Extractor", "Chaos-Heros-Online-Extractor.csproj", "{76FF8A9F-135D-4B0E-8A5B-0BAE7F093812}"
+Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "Chaos-Heroes-Online-Extractor", "Chaos-Heroes-Online-Extractor.csproj", "{76FF8A9F-135D-4B0E-8A5B-0BAE7F093812}"
 EndProject
 Global
 	GlobalSection(SolutionConfigurationPlatforms) = preSolution

Program.cs

@@ -1,6 +1,6 @@
 using System.IO;
 
-namespace Chaos_Heros_Online_Extractor
+namespace Chaos_Heroes_Online_Extractor
 {
     class Program
     {