Provided is a network system including at least first and second communication terminals capable of communicating with each other via a network. The first communication terminal causes handwritten data input in response to an instruction for a point on an image to be displayed in a certain position on the image corresponding to this point, associates the point information about the point with the handwritten data and transmits the point information and the handwritten data to the second communication terminal. Based on the point information and the handwritten data from the first communication terminal, the second communication terminal causes at least a part of the image to be displayed on a second display and also causes the handwritten data to be displayed in a location in accordance with the point information.