A booster lever unit includes a first lever pivotably supported by an object via a first pivotal shaft, a second lever pivotably supported by the object via a second pivotal shaft, and a linkage member that links the first lever to the second lever. The pivotal plane of the first lever is parallel to the pivotal plane of the second lever. The first lever has one end provided with an operation section, and another end provided with the first pivotal shaft, and the first lever further includes a first linker, the first linker being provided between the operation section and the first pivotal shaft and linked to the linkage member. The second lever has one end provided with an action section, and another end provided with a second linker linked to the linkage member, and the second pivotal shaft is provided between the action section and the second linker.

A plug connector to be plugged along a plug-in direction into a mating plug connector having a mating plug connector housing. The plug connector includes a plug connector housing; electrical contact elements, which are situated in the plug connector housing; a first lever system to reduce an operating force when the plug connector is plugged into and/or released from the mating plug connector, the first lever system being rotatably supported on the plug connector housing, the first lever system having: first and second arms, the second arm being pivotably situated on the first arm using a first joint pin, the first joint pin being movable in the plug connector housing in a first guide slot, which essentially extends along the plug-in direction, a first guide system between the first arm and the plug connector housing, and a second guide system between the second arm and the plug connector housing.

A connector member including an unlocking mechanism, the connector member includes: a base that is attachable, on one end side in a length direction, to a connector main body having an elastic locking piece for locking, which protrudes in a cantilever shape; a manipulation lever that is pivotally supported on an outer surface of the base in a see-saw movable state and extends in the length direction; and a release lever that is pivotally supported on an outer surface of the base in a see-saw movable state and extends in the length direction.