The barrier (関所,Sekisho?) is an area of the village. Alongside seventeen of the casual villager force, two Chainsaw Sisters were also part of the defensive force.
It appears to be a camp full of Ganados though a mining area can be seen at the back. There are two dumpsters which Ashley can hide.
Upon entering the area there is a dumpster to your right that Ashley can hide in. Once she is safely hidden in the dumpster proceed up the ladder in front of you or take the pathway to your right and head up the ladder at the end of the pathway, proceed to kill all Ganados on top of the structure. Once the area is cleared jump down into the pit in the middle of the structure it has ladders on either side, do not kick them down as you may need them if you have to make a quick escape from the Bella Sisters or Chainsaw Sisters. Immediately after jumping down a short cutscene will play showing the Chainsaw Sisters appearing and proceeding to attack the player. Once the cutscene is over you must kill whichever Chainsaw Sisters holds the Campsite key while the other will drop a Ruby worth 10,000₧ at a merchant. Once the chainsaw sisters are dead and the camp key is obtained, proceed through the door located in the pit where the sisters were encountered through the door is a pathway which will lead to multiple Ganados kill them then proceed to the red door at the back of the area to progress onwards.
The camp door while it is locked
(locked door sound) It won't open. It's locked. The shiny thing hanging from that hag's neck must be the key for this door.
The door to the Lift
(view door and wood bar disappearing) You've unbarred the gate.