The border cities and ports that separate the Yamato Republic from the Gray Zones typically consist of two parts – gang-controlled slums and the port control authority. Ever expanding criminal influence presents a great challenge to peace and stability, hence the Yamato authorities deploy the Kyoukai Shield Forces (KSF) to patrol the boundary zones between government and gang-controlled neighborhoods. Typically consisting of two to three KSF Sentinels led by a KSF Sergeant, KSF squads are armed with enough heavy gear to quell a formidable gang-backed insurrection.

KSF are part of the warrior caste who enjoy considerable benefits as long as they remain in service and maintain an acceptable fitness score in the quarterly national health check. Those with high fitness scores, ample battle experience and the right connections are promoted to become sergeants, and may eventually qualify to join the prestigious samurai caste. Those who do not pass the health check are relegated to demotion or outright expulsion from the warrior caste.

大和共和國與戈雷區之間的港口與邊緣城市，通常分屬於控制貧民窟的幫派和港口管理局。這些地方不斷擴大的犯罪影響衝擊著國內局勢的和平與穩定。為此，大和政府特意將境界部隊部署在與幫派地盤相鄰的區域巡邏。境界部隊中的每個小組由境界軍曹和兩至三名境界兵衛構成，配備重型武器和先進裝備，會以最快速度平息幫派鬥爭引起的衝突。

境界部隊也屬於武士階層的一部分，只要繼續服役並在每季度的國民健康審查中保持一定分數，便可持續享受可觀的福利。那些健康值高、戰鬥經驗豐富且有良好人際關系的，將被提拔為軍曹，並獲得進入最高武士階層的機會。而那些沒有達到健康審查標準的，則會被降級甚至被驅逐出武士階層。