You can watch a clip of the segment here.
According to Soompi, Luna said that she hadn't seen Sulli after she left f(x) in 2015 and said: “[When I heard the news of her passing], I sat down in the street and cried. She contacted me [before she passed away]. For the first time in 15 years, she used informal speech with me and said, ‘Unni, I want to see you.’ I could tell that it was a message that she sent after holding it in for a long time. I felt so apologetic as her unni. I should have approached her first to talk. I should have said something, I should have told her I loved her more.”
Luna also talked about losing her close friend and roommate, who died not long after Sulli, as well as her own depression and panic disorder. After the segment was broadcast, she thanked fans for their support and positive responses and revealed that she is "working hard on preparing my next album" and has "plans to continue doing musicals."