A game server device (3) stores message information representing contents of a message sent by a player and a card ID identifying each of a plurality of players in association with each other. Each of plural game devices (1) reads from a card (2) a card ID for transmission to the game server device (3), receives individual information corresponding to the card ID for storage, and transmits the individual information to an opponent participant's game device (1) so that the information is stored therein. Each game device (1), in a case in which an event is detected, displays a message represented by individual information that has been stored and requests an opponent participant's game device (1) to display the message. Furthermore, each game device (1), in a case in which the display of a message is requested from an opponent participant's game device (1), displays a message represented by individual information that has been stored.