Provided is a connector including: a plug to be attached to an opening of a liquid storing container and attached to an inner peripheral surface of the opening; a key ring to be attached to an outer peripheral surface of the opening extending along an axial line and including a key hole portion disposed at an outside of the outer peripheral surface with respect to the axial line; and a socket to be detachably attached to the plug and including a key rod portion to be engaged with the key hole portion. The plug and the socket are coupled together in a state where the key hole portion and the key rod portion are engaged with each other.