btw if you apply 'Average Normals - Near' on your VRoid model's mouth parts in PMX Editor (especially if it's cell shaded or has 2D look), you'll get this very nice looking outline around the mouth and on the tongue, but specifically on the edges of the teeth 😊
it's not mandatory to do so ofc, but it does give a pop up look on the teeth (would look much better w/o toon but that's just my preference!) also this can be easily done by just merging vertices with Blender/Metasequioa/any 3D modeling software you use, but this is mainly for MMD users who's only familiar with PMX Editor! (or any lazy bum like me HAHA)
anyway to do this, just go to this option as shown here:
it'll prompt you to enter your value; the default value is fine, but i prefer to use 0.000000001 for smoother look after that you're p much done!
if you wanna go extra, you can use Edge Scale tool (accessible from Vertex option) to manually adjust the outline value w/o needing to separate your mouth mesh to different materials 😄
