Recently, literally the day I release this app, I found this nice and complete toon shader for Unity: 夜空くらげ no X: "みんなliltoonのファーシェーダーが「「触れる」」こと知らないよね、ボクは知ってる https://t.co/MmLOHWCvBc" / X (twitter.com)

In short, it's a very complete shader called lilToon made by lilxyzw (github.com). It's a shader made for avatars in VRChat that actually works on the Mouse Tuber app, as long as the app has the shader files. Once its there, you can import the shaders yourself, create a material with the lilToon shader, and the app is able to load them without the need to include the whole shader in the asset bundle!

You can get the unity package here 【無料】lilToon - lilLab - BOOTH. Consider donating as well, it's 500 japanese yen.

Anyways, I will send the creator an email to make sure I can include the shader in the next build.