BACKGROUND AND SUMMARY
 There are conventional controllers capable of accommodating an information processing device therein. For example, there is a controller capable of accommodating a mobile telephone by means of a left key plate and a right key plate. Specifically, the controller includes a spring for sliding one key plate toward the other key plate so that the mobile telephone is sandwiched between the left and right key plates, thereby accommodating the mobile telephone.
 It is only the controller that includes a holding mechanism (i.e., the key plates), but the mobile telephone does not include a holding mechanism. Therefore, the controller can easily come off the mobile telephone.
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