>>41393364yeah basically but also the tatsumi port island incident that created Tartarus, or more specifically, broke the boundary between the real world and tartarus
probably, since p3, 4 and 5 have a shared world, also the reason for the existence of personas in those games
unless you get into the philemon thing and prefer the entire series being a continuous world but it sort of changes with the cognition thing in p5
Mementos is pretty much comparable to Tartatus but theres no explanation for its appearance besides the cognition thing and even Igor just says its cognition so it could be that they are completely separate universes in each game
i need to go and play the first 3 games because i dont know the specifics of its world.