A control system includes a session controller to control establishing a session for transmitting information between a communications terminal and other communications terminals, in response to a request from the communications terminal, and a start request receiver to receive, after a first session for transmitting information between a first communications terminal and a second communications terminal and a second session for transmitting information between a third communications terminal and a fourth communications terminal have been established, a communications start request for starting communications between the first communications terminal and the fourth communications terminal. When the start request receiver receives the communications start request, the session controller decouples the first session and the second session, and establishes a session for transmitting information between the second communication terminal and the third communications terminal and a session for transmitting information between the first communication terminal and the fourth communications terminal.