In the present invention, a game system includes a game program storage unit, a group information management unit, a play history storage unit, and a group information update unit. The game program storage unit stores a game program for executing a game to be provided to a plurality of terminal devices. The group information management unit stores player identification information identifying each of a plurality of players of the game and group identification information identifying a group which includes the player, in association with each other. The play history storage unit stores a play history of each of the plurality of players for the game. The group information update unit changes an association stored in the group information management unit between player identification information identifying a first player among the plurality of players and group identification information, at least partially in accordance with the play history of the first player.