1. A motion picture playing method for playing a motion picture image on a display unit, said method comprising: obtaining a first image; obtaining a second image; obtaining a motion picture image in which the second image serving as a background image is combined with the first image serving as a foreground image, wherein a position of the foreground image in the background image changes in the motion picture image over time; obtaining a character string to be scrolled and displayed in a predetermined direction overlaid on the motion picture image; and controlling a display mode for scrolling and displaying the character string based on (i) a length of the character string in the predetermined direction and (ii) a time required for changing the position of the foreground image in the motion picture image.