가 누군지

who … is

→ 가
phrase Common #3,449
who … is Follows a person’s name or pronoun to mean “who that person is.”
KO: 네가 누군지 이제 알겠어.
EN: Now I know who you are.

나 순이가 누군지 알아요

I know who Soon-i is.

— Space Sweepers (2021)