>>2863168>>2863175While I do heavily recommend learning the basics of Blender applicable to PMX modeling, PMXView > face select > Edit (E) > Face (F) > Truncate Separate Vertex (K) / Seperate [sic] Shared Vertex (V) > then prying them apart in UV editor (if necessary) will also do the job just fine. Beware that these functions split off every single face you've selected, so you might wanna merge unnecessary splits back with select vertices > Edit (E) > Vertex (V) > Join Vertex (Near) > OK to avoid bloating the model or incomplete selections (particularly when using Ctrl+X) in the future.