A communication system includes multiple communication terminals that are used by multiple users; and a management unit that holds management information expressing which type of communication mode corresponding to which communication address information is used by which user and by which communication terminal, and connection information including communication address information of one communication terminal that has communicated and communication address information of the other communication terminal that has communicated. The management unit holds connection information corresponding to an instance of communication even if that instance of communication has ended. Each communication terminal can communicate with other communication terminals in one or more types of communication modes, and includes a communication support unit.