A base station according to an embodiment is a base station included in a RAN of a mobile communication system. The base station includes a receiver configured to receive, from a radio terminal in a specific state, a message indicating that the radio terminal has left a RAN paging area, and a transmitter configured to transmit, to a mobility management entity, paging area information related to update of the RAN paging area in response to the reception of the message. The specific state is a state in which an anchor base station in the RAN paging area maintains an S1 connection for the radio terminal and the RAN paging area is configured to the radio terminal.