Persona 3 already has a social game, and now Persona 4 is getting one, too. Index have announced Persona 4: The Card Battle for the GREE social games platform.
In Persona 4: The Card Battle, you collect cards of characters from the Persona universe and do battle. That includes the Personas themselves, and Index say there are over 400 cards to collect.
Persona 4: The Card Battle will launch in September, but users can sign up for the game now.