1. A network system for assisting sales promotions in at least one eating and drinking establishment, the network system comprising: a reader having a communication interface and memory installed in an eating and drinking establishment, the reader storing reader identifying information, and transmitting reader identifying information, visit information, and user identifying information; a first server having a first processor and a first memory operatively coupled to the first processor; and a second server having a second processor and a second memory operatively coupled to the second processor; the first processor being programmed to: store visit information and incentive information in the first memory; in response to a user terminal being brought in contact with or in close proximity to the reader, retrieve visit information including at least user identifying information and reader identifying information from the user terminal or the reader, and store the visit information in the first memory; and update the incentive information in the first memory when: (i) information for exchanging an incentive for an item is received from the user terminal and sent to the second server, and (ii) a notification of exchange process completion is received from the second server; and the second processor being programmed to: retrieve item information from the first server; store the item information in the second memory for an application service corresponding to individual users, the item information including user identifying information and password information of the user; perform an authentication process of verifying whether the user identifying information and password information of the user is permitted; and if permitted by the authentication process and in response to the retrieved item information, send a notification of the exchange process to the first server after the item exchange process has ended, such that the item information is updated in the first memory, and a number of the item is added in proportion to a number of exchange process completions, wherein if the user terminal is not capable of transmitting or receiving information from the reader, the reader plays a predetermined sound unique to each reader or to each eating and drinking establishment that is detected by the user terminal such that the user terminal identifies the reader or the eating and drinking establishment based on the predetermined sound, and upon recognizing the predetermined sound played by the reader, the user terminal transmits reader identifying information, user identifying information and time information to the first server.