A memory card system includes a host that issues a read command and a memory card that upon receiving the read command sends read data to the host in synchronism with a read clock signal generated within the memory card. The method includes closing an opened session by closing all opened sequential recording-units of the opened session, opening a new session having a new sequential recording-unit, and recording session start information on the recording medium. The second engagement portion is disposed inboard from the first engagement portion in the axial direction of the image carrier. LixMyOz\u2003\u2003Chemical Formula 1Li+RCOO\u2212\u2003\u2003Chemical Formula 2.