A lever (11) swings from a fitting start position to a fitting completion position on a housing (10) and has a cam groove (68). In the swinging process, a cam follower (21) of a counterpart housing (14) and cam (55) of a moving plate (13) advance a fitting operation between the housings (10) and (14) to move the moving plate (13) from a moving start position to a moving completion position. A detachment regulating portion (69) locks the cam (55) at the fitting start position to regulate detachment of the moving plate (13) from the hood (26). The lever (11) is swung from the fitting start position in an opposite direction of the fitting completion position, and has a detachment allowing position separating the cam (55) from the detachment regulating portion (69) to allow the moving plate (13) to detach from the hood (26).