A history-information obtaining unit obtains operation history information from a plurality of player terminals. A feature-information generating unit generates, for each of a plurality of players, feature information representing a feature of operation in the form of a certain weighted value obtained from the operation history information. A clustering unit clusters the plurality of players on the basis of the individual feature information of the plurality of players. An other-player-information sending control unit executes control so as to send information about other players belonging to the same group to the individual player terminals of the clustered plurality of players, while prohibiting sending of information about other players belonging to other groups.