bodyguard; imperial guard
Historical term for a guard or bodyguard, especially in an imperial or noble context. In modern Japanese, ボディーガード is far more common for a personal bodyguard.
The imperial guard was responsible for protecting the emperor's person.
In this novel, the protagonist serves as a bodyguard for a noble.
captain of the guard
Compound of 侍 (samurai, attendant) and 衛 (guard, protect). The exact historical derivation is uncertain; the word is now rare and largely replaced by modern terms.