To allow anonymous log-in without registration of personal information in an affiliated site providing a chargeable network service.

A biometric authentication device allows log-in to a management site when biometric authentication of a user is verified. A communication terminal apparatus transmits site specification information specifying the affiliated site accessed by the user to the management site in predetermined timing. The management site generates a one-time code and transmits it to the communication terminal apparatus and the affiliated site when the site specification information is transmitted. In receipt of the inputted one-time code, the affiliated site compares the received one-time code with that transmitted from the management site. When both one-time codes agree with each other, offer of the network service is started, and billing information matching the one-time code is generated to be transmitted to the management site.