expression, noun
head of a household; business owner; proudly independent person
Modern figurative use: someone who is the master of their own domain, whether a home, a small business, or a personal sphere, with a sense of proud independence.
定年後は小さな店を開いて、一国一城の主として気ままに暮らしている。
After retirement, he opened a small shop and lives freely as the master of his own little domain.
彼は家では一国一城の主だ。
At home, he is the lord of his own castle.
expression, noun
Historical literal meaning: a lord who ruled a single castle and its domain. Now used mainly in historical contexts or as the origin of the modern figurative sense.
戦国時代、一国一城の主として領地を治めることは大名の証だった。
In the Warring States period, ruling a domain as the lord of a single castle was a mark of a daimyo.
Literally 'lord of one country and one castle'. Originates from the feudal era when a daimyo held a single castle and its territory. The modern figurative sense extends this to anyone who is the undisputed master of their own small domain.