A mobile station that establishes a first transfer path by way of a first access network between the mobile station and a control station. The mobile station establishes a default EPS (Evolved Packet System) bearer by way of a second access network between the mobile station and the control station by transmitting an attach request for requesting a handover of a partial flow among the plurality of flows when performing transmission/reception of a plurality of flows with the control station by using the first transfer path.