A radio terminal (3) has a function of establishing a second radio connection on a second cell (20) operated by a second radio station (2) while a first radio connection on a first cell (10) operated by a first radio station (1) is established. The first radio station (1) sets up a control bearer for transferring at least a control signal regarding the radio terminal (3) between an upper network (4) and the first radio station (1). Further, the first radio station (1) is configured to trigger setup of a second bearer for transferring user data of the radio terminal (3) between the upper network (4) and the second radio station (2). It is thus for example possible to enable a single radio terminal to simultaneously set up bearers on cells of a plurality of radio stations, in order to achieve carrier aggregation of cells operated by different radio stations.