A fan club is a group that is dedicated to a well known or popular person, group, idea, or object. Most fan clubs are run by fans, for fans, who devote considerable time and resources to supporting them. There are also "official" fan clubs that are run by someone associated with the person or organization the club is centered around, as opposed to "unofficial" where the club owners are not directly linked to the target of fandom.
Four fan clubs exist in Crisis Core, one for Angeal Hewley, one for Sephiroth, and two for Genesis Rhapsodos, one more concerned with his LOVELESS research and the other with Genesis as a whole. Depending on Zack Fair's actions during the game, a fan club for him can be started, and the two Genesis fan clubs can merge. The player can join all the clubs during the game to receive special emails from them.