Chat System, Server Device, Chat Method, Chat Execution Program, Storage Medium Stored with Chat Execution Program, Information Processing Unit, Image Display Method, Image Processing Program, Storage Medium Stored with Image Processing Program

A matching server, when a chat room specified by participation request information received from a client terminal device is registered in a room storage region, associates and registers that client terminal device to the chat room, and when the chat room specified by the participation request information is not registered, associates the client terminal device and the chat room with each other and registers them newly in the room storage region. When a chat room specified by leave request information received by the client terminal device is registered in the room storage region, it cancels registration of the client terminal device for the chat room, and when there is no client terminal device registered to the registered chat room, it cancels registration of the chat room.