Actually, I'm not sure a crossover with 'Persona' always needs to blend entire game worlds to work. The most effective ones I've seen focus less on literal universe collision and more on transplanting the core psychological mechanics into another setting. Like, there's this fantastic 'Persona 5'/'Cyberpunk 2077' fic where the Phantom Thieves' heists target corrupt corpos' Palaces within the Braindance network. It didn't bother merging Tokyo and Night City geographically; it just asked, 'What if the Metaverse existed as a layer in Cyberpunk's tech?' That feels way more authentic than trying to force a fusion of realms.
Sometimes writers get tangled up explaining how Igor's Velvet Room now exists alongside, say, the Jedi Temple, and it bogs everything down. The blend works best when the 'Persona' elements—themes of self-discovery, confronting inner shadows, and using a manifested self—act as a new lens on the crossover world's conflicts. A good crossover uses one world's rules to illuminate the other's characters in a fresh way, not just smash two maps together.