Refers to the system of monarchy or the monarch's realm. Rare and literary; in modern Japanese, 君主制 (くんしゅせい) is the standard term for monarchy.
monarch and nation
Emphasizes the unity of the sovereign and the state. Rare and archaic; not used in everyday speech.
The word 君国 sometimes refers to monarchy in old texts.
The idea of the unity of monarch and nation is found in pre-modern political thought.