Radio terminal and base station

A user equipment for a mobile communication system, includes: a receiver configured to receive, from a base station, an RRC (Radio Resource Control) connection release message including information instructing a transition to a specific state; and a controller configured to cause the user equipment to transit to the specific state in response to receiving the RRC connection release message including the information. The specific state is a different RRC state from an RRC connected and an RRC idle, and a connection for the user equipment is maintained between the base station and a core network.