A game machine 1 is provided with progress state controlling means 21 for storing and controlling a state of a progress of a story in a game for each player, player identification means 15 for identifying the player on the basis of an origin of a received mail received through a receiving server 12, instruction obtaining means 16 for analyzing contents of a sentence of the received mail so as to obtain as instruction information, story processing means 18 for judging the state of the progress of the story corresponding to the player identified and for processing a development of the story in the game on the basis of the judged state of progress and the instruction information, reply mail preparing means 19 for preparing a reply mail for sending information in response to the instruction information on the basis of the processed development of the story, and reply mail processing means 20 for sending the prepared reply mail to the identified player through the server 13.