As Sengoku Daimyo (feudal lords) established their sovereignty, they made their Kokujin Ryoshu (local samurai lords) in various provinces live within the castle towns in order to ensure that the latter was completely obedient to the former.
戦国大名が支配権を確立するにつれ、各地に割拠していた国人領主などを完全に家臣として組み込むにあたり、城下町に集住させるようになった。