Content displayed in an area displayed by a native application can be changed without being updated by a user. A first image is generated on a communication terminal (20) in response to launching of an application installed on the communication terminal (20) and is displayed in a first area on a screen of the communication terminal (20). An image generator (16) generates a second image displayed in a second area differing from the first area. The image generator (16) also generates a third image displayed in a third area included in the first area. A server (10) displays the second image in the second area on the screen of the communication terminal (20) and displays the third image by overlaying the third image on the first image in the third area included in the first area on the screen of the communication terminal (20).