chief guard; warden
Refers to the head of prison guards or the person in charge of a prison's security staff. In some contexts, it can be translated as 'warden', though the exact responsibilities may differ from the English term.
The chief guard explained the rules to the prisoners.
After many years of service, he was promoted to warden.
Compound of 看守 (かんしゅ, 'prison guard') and 長 (ちょう, 'head, chief').