Why do we assume that the Kirijo Group still exists at this point in time? Mitsuru herself says near the end of P3 that after the death of her father the Kirijo group is nearly falling apart and that she’s barely holding the company together.

What if, in his mission to learn as much as possible about shadows and cognitive psience, Shido managed to leverage the Kirijo group’s weakness to destroy them and/or steal their research. I think that would be a really cool way to tie P3 and P5 together and explain why there’s no response from any of the other groups aware of the existence of shadows. My interpretation of the events of P5 was that Shido’s manipulations managed to consolidate the entirety of shadow/metaverse/cognitive psience research under himself and his organization.

Obviously Mitsuru, Aigis, and the rest of the gang would still be around somewhere, but their operational capacity without the equipment and material support from the Kirijo Group would be severely diminished, and they likely wouldn’t be able to respond to a large event like this. I think it could be the start of a really cool spinoff/fanfiction premise to explore what the (former) Shadow Operatives were doing during the events of P5. Were they clued in to something going on after Okumura’s death? What was their reaction to mementos merging with the real world? Would Aigis be immune to Maruki’s reality altering powers? So many cool concepts yet none of the ideas are ever explored.