sankin-kōtai was a policy implemented during the Edo period in Japan, requiring feudal lords, or daimyō, to alternate their residence between their home domains and the capital, Edo. This system aimed to strengthen the central government's control over the daimyō and reduce the risk of rebellion by keeping them away from their power bases. Under this policy, daimyō had to maintain a lavish household in Edo, which contributed to the economy and culture of the city. The system also ensured that the daimyō's families remained in Edo as hostages, further securing loyalty to the Tokugawa shogunate.