An information processing system including: a storage section that stores information about a plurality of agents capable of dialogue with a user, each agent having different attributes; a communication section that receives a message from the user from a client terminal, and also replies to the client terminal with a response message; and a control section that executes control to select a specific agent from the plurality of agents, according to an instruction from the user, record attributes of the specific agent updated according to dialogue between the specific agent and the user as the attributes of a user agent, specify a partner user who most resembles the attributes of the user agent by comparing the attributes of the user agent and attributes of a plurality of actually existing partner users, and notify the user of the existence of the partner user at a predetermined timing.