Word of advice:
Devil Survivor 2 turns downright evil at the final day (of your first playthrough). In any important battle, let the MC destroy bosses and high-level enemies the most so that his level unlocks more fuseable demons because the free battles will be incredibly slow level grinding. If you can let your party members get experience through free battles, let them.
Also, crack skills, crack, crack, CRACK. If you come across Recarm and Samarecarm, GET THEM IMMEDIATELY. The quick-turn revive strategy is no longer here, but even so, having those revive spells around are a must.