noun
one's own domain; independent territory; being one's own master
Figurative use: acting independently, without compromise or outside help, as if one were a feudal lord with one's own castle and domain. Often used in phrases like 一国一城の主.
彼は会社の中で一国一城の主として振る舞っている。
He acts like the lord of his own castle within the company.
His dream is to become independent and build his own domain.
noun
one castle per domain; 1615 edict limiting castles
Historical term referring to the shogunate's 1615 edict that each feudal domain could have only one castle. Rare outside historical contexts.
一国一城令は1615年に出された。
The edict of one castle per domain was issued in 1615.