A radio communication system includes a mobile terminal device to which a memory card is attached and a server device. The server device and the memory card transfer information to each other through the mobile terminal device by radio communication. This is achieved in the following manner. When receiving a start request from the server device, the mobile terminal device supplies power to the memory card. Furthermore, the mobile terminal device communicates with the server device, to prepare for information transfer to be performed between the server device and the memory card. After becoming able to operate, the memory card performs a boot operation. When completing the boot operation, the memory card starts information transfer with the server device through the mobile terminal device.