After MINAMOTO no Sanetomo was assassinated, Kozamurai dokoro (the Shogun's guard) was set up, and a system of Koban (small watch teams) was created, which consisted of 6 teams on a rotating 24 hour watch.
源実朝の暗殺後、小侍所が設置され、6番制によって1日1番の小番が編成された。