1. A connector configured to be mounted on an end portion of a flat cable, the connector comprising:a stage having an arrangement surface for arranging the end portion of the flat cable;
an engaging protruding portion formed on the arrangement surface for engaging the flat cable;
an opposing portion formed so as to face the arrangement surface; and
two side wall portions positioned on opposite sides from each other in the left-right direction to interpose the arrangement surface,
wherein the end portion of the flat cable is insertable from a front side of the connector to a rear side of the connector between the arrangement surface and the opposing portion, wherein the opposing portion has a first section arranged in front of the engaging protruding portion and a second section extending rearward from the first section, wherein the first section has a connecting portion connecting to at least one of the two side wall portions, and wherein the opposing portion is elastically deformable to allow the second section to move vertically around the connecting portion.