Because Young-goon was raised by her grandmother, she speaks in a sort of "old-fashioned" way. So the titles portraying "uns" as an analog for "ones" is to show that she has an unusual way of speaking. This seems to be a trademark for Park Chan-Wook.

Yes, it does mean "ones" (presumably Korean has a common standard way of transforming adjectives to nouns describing people featuring that quality) but the "one" here is not the third-person singular generic human pronoun as in "One does such-and-such." Pronouns cannot be modified by adjectives (such as "white") or pluralised with "-s", and "one" as used here can be applied to humans, animals or objects. It's just a very non-specific noun, so much so in fact that it cannot be used without an adjective or equivalent modification.

Just to clarify, "'uns" is a colloquial/vernacular way of saying "ones" which is used as an English analogue for a word in the Korean. So you should try to find an analogue for this in the language you're translating to; if you find that you can't, then just use the analogue of "one" (i.e. the third-person singular generic human pronoun).

I'm from Manchester and I frequently hear "'uns" added after other words, in fact my dad calls my niece "little 'un" meaning little one, and like DarkDon says, there's "young 'un" (young one), "big 'un" (big one) and so on. I too found it odd - and strangely gratifying - to see it appear in a Korean film!
-"There's no such thing as trolls."
-"Then how do you explain all the dead unicorns?"

i believe it was doctors & nurses. i didn't get it at first but after watching it a second time that's the only conclusion that made sence.

He he he, Im From yorkshire and my grandparents always used to reffer to my and my brother as the "Young 'Uns", thought it was really odd when i saw the expression come up in this Korean film!
Anywhoo, advise in no way helpful but thats my two cents!

it might be. and they all are dressed in white. thanx
yes, i am translating from english subtitles.

According to the English subtitles she calls them "White 'uns," which I always assumed meant "White ones" (because they all wear white coats) and she was just saying it in a strange way. Sort of like a little kid might. I don't know Korean so I could be wrong, but that's how I interpreted the English subtitles.