Visit the Climax Theater in Persona 2: Innocent Sin and you can enter visit the world of Shin Megami Tensei If…. A quest called "The Persona Robber" made just for the PSP version takes players to Karukozaka High where students lacking ambition wander the halls.
This quest also gives players access to two new personas, Persephone and Kushiel.
Yes, the romanization Atlus posted is "Chushiel," but I’m pretty sure it’s Kushiel, an angel and one of the Seraph class demons from a previous Shin Megami Tensei game. Persephone was a Reaper class demon in Shin Megami Tensei: Strange Journey with wind spells like Magarudyne. In Persona 2: Innocent Sin she can cast Gryva, a gravity attack.