We don't have CR yet, but I thought it might be good to fill this out preemptively anyway! :)

Character: Mitsuru Kirijo
Can Fitz manipulate how they perceive him? Yes, go for it! No permission needed-- if I'd rather not roll with something, I'll let you know and we can say it was ineffective or something, but it's unlikely.
Could they mistake Fitz for someone else? YES this sounds fun.