Abstract: An object storage unit (220) stores object information, including that of a main character who wears a camouflage outfit. More specifically, the object storage unit (220) stores a standard texture (222) showing a standard camouflage pattern, an additional texture (223) showing a replaceable camouflage pattern, as well as a material properties parameter (224) that determines the material properties of the camouflage outfit. When the main character stops, a background specifying unit (232) specifies the object serving as the background of the main character by referring to a position information storage unit (240). In addition, a clothing changing unit (233) appropriate selects a combination of an additional texture (223) and a material properties parameter (224) according to the texture or other features of the specified object, thereby changing the appearance of the main character's camouflage outfit.