Mystia.Extension.Sdk 1.0.0

Mystia Extension Framework

Unofficial mod middleware for Touhou Mystia's Izakaya. Launching the game directly still runs the Steam copy unchanged. Mods start only when the game is launched through Mystia.Syringe.

This project does not ship the game, its assemblies, or generated interop. Those stay on your machine.

Supported build: Unity 2021.3.28f1. GameAssembly.dll SHA256 91CE5AE3DAD5DA07DFED63BAB4C9E454F67B6E50F9A6E8EC498EF9B0B806A789. A different game build will not start.

Mod authors

Install the .NET 10 SDK. Reference the package Mystia.Extension.Sdk.

<Project Sdk="Mystia.Extension.Sdk/1.0.0">
  <PropertyGroup>
    <TargetFramework>net10.0</TargetFramework>
    <MystiaInteropDir>C:\path\to\artifacts\interop\</MystiaInteropDir>
  </PropertyGroup>
</Project>

MystiaInteropDir must point at interop assemblies generated from your own game install. The public scene, listener, and service APIs use game types, so the compiler needs those assemblies. This repository's nuget.config also looks in artifacts/nuget after you pack the SDK locally.

Generate interop and the id catalog by passing the game project directory. Interop also needs the Steam install directory. There is no default path.

dotnet run --project src/Mystia.CatalogGen -- <game-project-dir>
dotnet run --project src/Mystia.InteropGen -- <game-project-dir> <game-install-dir>

The project directory is the game repository root. Catalog generation reads Assets/_SortedAssets/DataBase. Interop generation reads the Managed folder under Build/Symbols, and GameAssembly.dll plus global-metadata.dat from the install directory.

A mod is a class library. Declare one type per behavior, mark the interfaces with [AutoWire], and add mod.json next to the assembly:

{
  "id": "sample.a",
  "version": "1.0.0",
  "loadAfter": []
}

loadAfter is not an order. Players set the order in launcher.json with modOrder. Listed ids run in that sequence. A loaded mod missing from the array runs afterwards, sorted by id.

Namespaces:

IModContext.LoadSprite loads a PNG from a path relative to the mod directory. Catalogs.Core.FoodTags.Meat and the other Catalogs members are the stock ids, with Chinese summaries on each constant.

Scene loops implement Setup, Update, and Shutdown. The services argument is valid only inside those calls. SceneId.Night is the work scene (IWorkSceneGameLoop).

See samples/SampleMod.A, samples/SampleMod.B, and samples/SampleMod.Skip.

Players

Install the .NET 10 runtime. The launcher directory contains:

• Mystia.Syringe.exe
• Mystia.Bootstrap.dll
• launcher.json
• mods/, one folder per mod with that mod's dll and mod.json
• host/Mystia.Modding.Host.dll, host/Mystia.Modding.Host.runtimeconfig.json, and the host's dependencies, including the bridge, Il2CppInterop, and HarmonyX

launcher.json:

{
  "gameExe": "C:\\Path\\To\\Touhou Mystia Izakaya.exe",
  "modsDirectory": "mods",
  "expectedGameAssemblySha256": "91CE5AE3DAD5DA07DFED63BAB4C9E454F67B6E50F9A6E8EC498EF9B0B806A789",
  "modOrder": ["sample.b", "sample.a"]
}

gameExe is required. If GameAssembly.dll beside that executable does not match expectedGameAssemblySha256, the game is not started. The injector does not write into the Steam directory.

Windows security software often blocks a program that starts another process suspended and loads a DLL into it. That is how the injector mounts mods.

Build the managed launcher from this repository with dotnet build src/Mystia.Syringe. Build Mystia.Bootstrap.dll from native/Mystia.Bootstrap with CMake and MSVC. Publish the host with dotnet publish src/Mystia.Modding.Host -c Release -r win-x64 and copy the output into host/.

Pack the SDK

From the repository root:

dotnet pack sdk/Mystia.Extension.Sdk/Mystia.Extension.Sdk.Pack.csproj -c Release

The package is written to artifacts/nuget.

Third-party notices

Mystia Extension Framework is MIT, copyright 2026 Delsin-Yu. See LICENSE.

The bridge uses Il2CppInterop and HarmonyX, both MIT and copyright BepInEx contributors, and Iced, MIT and copyright 0xd4d. Those packages remain under their own licenses.

Trademark

Touhou Mystia's Izakaya and related names belong to their owners. This repository is not affiliated with them.