An example accessory can be attached to an information processing device. The accessory includes a housing, a movable operation section, and a movable portion. An inside of the housing is visible from an outside thereof through at least a portion thereof. At least a portion of the operation section is exposed on the outside of the housing. The movable portion is placed at a position inside the housing that is visible from the outside of the housing through the portion of the housing. A position and/or an attitude of the movable portion changes in response to the operation section being operated.