This is something I remember being mentioned in some other thread a while ago, but it was never followed up on.
Would it be warranted to make a demon_(smt) tag? It would be the Shin Megami Tensei equivalent to pokemon (creature), digimon (Creature), and duel monster, and it would follow the same rules (only to be used when a demon is physically present in picture, not merely depicted or cosplayed as).