A communication terminal comprising: a first client part configured to be enabled by starting in the communication terminal a first communication application for causing the communication terminal to perform a communication control function for sending stroke data to a first communication terminal, and an image processing function for outputting the stoke data as an image, wherein the first client part is configured to send content data; and a second client part configured to be enabled by starting in the communication terminal a second communication application for causing the communication terminal to perform a communication control function for sending display data to the first communication terminal, wherein the second client part is configured to send content data, wherein the communication terminal further comprises: a first communication control unit of the first client part configured to control a communication between the communication terminal and the first communication terminal via a delivery server; a second communication control unit of the second client part configured to control a communication between the communication terminal and a second communication terminal; an acquisition unit configured to acquire content data transmitted between the communication terminal and the second communication terminal in the communication controlled by the second communication control unit, the first communication control unit sending the content data acquired by the acquisition unit to the delivery server; and a display control unit configured to control a display of an image based on content data delivered by the delivery server, wherein the content data delivered by the delivery server include first content data sent by the first communication terminal and second content data acquired by the acquisition unit and sent to the delivery server, and wherein the display control unit is configured to perform a control of superposing the first content data and the second content data and displaying the superposed content data, wherein the first content data include stroke data and the second content data include stroke data. a first client part configured to be enabled by starting in the communication terminal a first communication application for causing the communication terminal to perform a communication control function for sending stroke data to a first communication terminal, and an image processing function for outputting the stoke data as an image, wherein the first client part is configured to send content data; and a second client part configured to be enabled by starting in the communication terminal a second communication application for causing the communication terminal to perform a communication control function for sending display data to the first communication terminal, wherein the second client part is configured to send content data, wherein the communication terminal further comprises: a first communication control unit of the first client part configured to control a communication between the communication terminal and the first communication terminal via a delivery server; a second communication control unit of the second client part configured to control a communication between the communication terminal and a second communication terminal; an acquisition unit configured to acquire content data transmitted between the communication terminal and the second communication terminal in the communication controlled by the second communication control unit, the first communication control unit sending the content data acquired by the acquisition unit to the delivery server; and a display control unit configured to control a display of an image based on content data delivered by the delivery server, wherein the content data delivered by the delivery server include first content data sent by the first communication terminal and second content data acquired by the acquisition unit and sent to the delivery server, and wherein the display control unit is configured to perform a control of superposing the first content data and the second content data and displaying the superposed content data, wherein the first content data include stroke data and the second content data include stroke data. a first communication control unit of the first client part configured to control a communication between the communication terminal and the first communication terminal via a delivery server; a second communication control unit of the second client part configured to control a communication between the communication terminal and a second communication terminal; an acquisition unit configured to acquire content data transmitted between the communication terminal and the second communication terminal in the communication controlled by the second communication control unit, the first communication control unit sending the content data acquired by the acquisition unit to the delivery server; and a display control unit configured to control a display of an image based on content data delivered by the delivery server, wherein the content data delivered by the delivery server include first content data sent by the first communication terminal and second content data acquired by the acquisition unit and sent to the delivery server, and wherein the display control unit is configured to perform a control of superposing the first content data and the second content data and displaying the superposed content data, wherein the first content data include stroke data and the second content data include stroke data.