Origin of a name

I live in Tokyo, and I recently found out that a friend of a friend, who I'd previously assumed was Japanese, was absent from an event because her visa ran out and she had to return to her home country for a while to get it sorted out.

Now I'm extremely curious as to what country she's from! Any idea where the family name "Zono" might be from? Or if not a family name, a given name? (I assume it's her family name, as everyone calls her ゾノさん, but stranger things have happened)

She always looked Japanese to me, so any chance it's some other East-Asian name? *terribly curious now*