Uhh.... who's Kim? Was he mentioned before?

Kim was mentioned near the very beginning when Hwijae met his father again. His father "misunderstood" that Hwijae was the whistleblower/spy from Ark, who is called Kim, due to his lack of identification and etc. But later on, we find out that Kim is actually female, and the father knew that Hwijae was someone suspicious from the very beginning but just wanted to keep him close~

In the first timeline, she went missing and still is in the current timeline.