Exemplary communication system 1 includes game devices 10, communication terminals 20, and game support server 30. Game devices 10 enable users to perform a multi-play activity. Each of communication terminals 20 runs an application associated with corresponding game device 10. Game support server 30 divides communication terminals 20 into separate communication groups in accordance with a situation of the multi-play activity performed by game devices 10 so that communication terminals 20 belonging to a same communication group can communicate with each other.