Superintendent
Administrator, Custodian
noun
Remember how 管理 is "management"? Well, a management person is someone who manages a place, like the superintendent for a building or park, or the administrator of a website.
It can also refer to someone who is appointed to manage an estate, like a property custodian.
This is a jukugo word, which usually means on'yomi readings from the kanji. If you know the readings of your kanji you'll know how to read this as well.
このウェブサイトの管理人は私です。
I am the administrator of this website.
うちのアパートの管理人さんは、いつも笑顔であいさつをしてくれる。
The manager of our apartment always greets us with a smile.
行方不明の方の財産を管理する人のことを「不在者財産管理人」と言います。
The person who manages the property of a missing person is called an “Absentee Property Administrator.”
「相続財産管理人」は、相続人がいない場合に代わりに財産を管理する人のことだけど、確か数年前に名称が変わってるはずだよ。
The term souzoku-zaisan-kanrinin (estate administrator) refers to someone who manages the estate on behalf of the deceased when there are no heirs, but I believe the name for it was changed a few years ago.