A mobile terminal device, comprising: a display configured to display a first display section including a first plurality of operation keys and to display a second display section including a second plurality of operation keys, the second plurality of operation keys displayed in the second display section based on a set of operation keys which are stored in memory, the set of operation keys being based on usage frequency; a touch sensor configured to receive a touch input corresponding to at least one of the first plurality of operation keys displayed in the first display section and the second plurality of operation keys displayed in the second display section; and a controller configured to switch the second plurality of operation keys displayed in the second display section to a third plurality of operation keys based on a predetermined moving touch operation received at the second display section, the second plurality of operation keys are assigned to a first page of operation keys and the third plurality of operation keys are assigned to a second page of operation keys, the controller is configured to control the display to switch from displaying the first page to the second page, and the controller is configured to control the display to display a page indicator in the second display section graphically indicating a position of a currently displayed page among a plurality of available pages of operation key display groups; and wherein the controller is configured to display a key of the second plurality of operation keys on the first and second page of operation keys in accordance with the usage frequency, wherein the controller is configured to replace a key of second plurality of operation keys with another key based on the usage frequency. a display configured to display a first display section including a first plurality of operation keys and to display a second display section including a second plurality of operation keys, the second plurality of operation keys displayed in the second display section based on a set of operation keys which are stored in memory, the set of operation keys being based on usage frequency; a touch sensor configured to receive a touch input corresponding to at least one of the first plurality of operation keys displayed in the first display section and the second plurality of operation keys displayed in the second display section; and a controller configured to switch the second plurality of operation keys displayed in the second display section to a third plurality of operation keys based on a predetermined moving touch operation received at the second display section, the second plurality of operation keys are assigned to a first page of operation keys and the third plurality of operation keys are assigned to a second page of operation keys, the controller is configured to control the display to switch from displaying the first page to the second page, and the controller is configured to control the display to display a page indicator in the second display section graphically indicating a position of a currently displayed page among a plurality of available pages of operation key display groups; and wherein the controller is configured to display a key of the second plurality of operation keys on the first and second page of operation keys in accordance with the usage frequency, wherein the controller is configured to replace a key of second plurality of operation keys with another key based on the usage frequency.