An information processing system that easily grasps the relationship between contents shared by communication includes a database that saves, in association with each other, a content identifier that identifies content data and a communication identifier that identifies communication performed in relation to the content data, and an associator that associates the first content identifier that identifies the first content data and the second content identifier that identifies the second content data by using a communication identifier that identifies communication performed between the first user and the second user when the first content data and the second content data are shared in relation to the communication.