1. A computer-readable storage medium, storing a character input program for inputting characters by using a pointing device having at least one button, wherein the character input program instructs a computer to function as: character input key image display control means for displaying, on a screen of a display device, a character input key image associated with a group of characters; pointed position detection means for detecting, based on a signal from the pointing device, a position on the screen being pointed at by the pointing device; button operation detection means for detecting whether or not the button is operated; undetermined character display control means for displaying one character on the screen as an undetermined character in a cyclic order from among the group of characters associated with the character input key image each time the operation of the button is detected by the button operation detection means while the pointed position detection means is detecting that the character input key image is being pointed at by the pointing device; and determined character display control means for displaying the undetermined character as a determined character on the screen when the position pointed at by the pointing device as detected by the pointed position detection means moves out of the character input key image associated with the undetermined character displayed on the screen.