When a player character has a raw stone material, a player can carry out material conversion at an arbitrary timing. In the material conversion, the player captures an arbitrary image in a real space or a virtual 3D space. RGB data of predetermined pixels are extracted from the captured image data, and average values for R, G, and B are acquired separately. A material of a type corresponding to the calculated average values of the RGB data is generated. When the player equips the player character with the material generated by the material conversion, magic corresponding to the equipped material can be used.