A processor provided with hardware is provided. The processor acquires user information of a plurality of the user terminals output from a store terminal that is provided in a store and executes payment settlement processing, generates, when a predetermined user terminal among the user terminals executes the payment settlement processing, group consumption information based on group information containing the user information of the predetermined user terminal and the user information of the other user terminals and consumption information associated with each of the user terminals contained in the group information, and generates payment information containing an allotted amount of the predetermined user terminal with respect to a target user terminal based on the group consumption information. The payment information contains information on a user ID of the predetermined user terminal, user IDs of the other user terminals, and the allotted amount.