A first mobile terminal requests a device to transmit data, on the basis of a processing request transmitted from a management server. The device transmits the requested data to the first mobile terminal. The first mobile terminal generates processed data by using the data received from the device. The first mobile terminal assigns an identifier to the processed data. The first mobile terminal transmits the processed data in association with the identifier to the management server. The first mobile terminal transmits an association relationship between the identifier and the data used for generating the processed data to the device. The device stores the identifier in association with the transmitted data. A second mobile terminal transmits to the device an identifier transmitted from the management server as an identifier associated with data to be deleted. The device identifies data associated with the identifier received from the second mobile terminal.