The pair met through 'Secret Unni', where Sunmi was Seulgi's 'secret unni'. They made an amazing pair on the show, and Sunmi even dedicated a song just for Seulgi called "Secret Tape" in her 2nd mini-album.
Seulgi showed that their friendship was still continuing. She was the 'ending fairy' for "Umpah Umpah" on 'Show! Music Core' on the 14th. For her ending, Seulgi did Sunmi's signature move from "LALALAY".
Check out the cute clip below.