To prevent a network response to a game server from deteriorating, a flag information management unit of a game server is provided. The flag information management unit manages flags indicating information on player characters (PC) in response to requests from client systems (or communication terminals)s occurring during network game progress. A flag information transmission unit transmits only the information linked to the managed flags to the client systems (or communication terminals). Then, on the sides of the client systems (or communication terminals), a control unit controls a CD-ROM drive in accordance with the information, and the necessary information is reproduced from a CD-ROM.